- Email: [email protected]
Catecholamines and cardiovascular disorders: Pathophysiologic considerations
de Feyter
74.
75.
76.
77.
78.
79. 80.
81. 82.
American
Gardner TJ. Unstable angina pectoris. Factors influencing operative risk. Ann Surg 1980;19:745. Rankin JS, Newton JR, Califf RM, Jones RH, Wechsler AS, Oldham HN, Wolfe WG, Lowe JE. Clinical characteristics and current management of medically refractory unstable angina. Ann Surg 1984;200:457-64. Rahimtoola SH, Nunley D, Grunkemeier G, Tepley J, Lambert L, Starr A. Ten year survival after coronary bypass surgery for unstable angina. N Engl J Med 1983;308:676-81. Cohn LH, O’Neill A, Collins JJ. Surgical treatment of unstable angina up to 1984. In: Hugenholtz PG, Goldman BS, eds. Unstable angina-current concepts and management. New York: Stuttgart: Schattauer, 1985:279-86. Goldman HE, Weisel RD, Christakis G, Katz A, Scully HE, Mickleborough LM, Baird RJ. Predictors of outcome after coronary artery bypass graft surgery for stable and unstable angina pectoris. In: Hugenholtz PG, Goldman BS, eds. Unstable angina-current concepts and management. New York Stuttgart: Schattauer, 1985319-29. McCormick JR, Schick EC, MC Gabe CH, Kronmal RA, Ryan TJ. Determinants of operative mortality and longterm survival in patients with unstable angina. J Thorac Cardiovasc Surg 1985;89:683-8. Luchi RJ, Scott SM, Deupree RH, et al. Comparison of medical and surgical treatment for unstable angina. N Engl J Med 1987;316:977-84. Nunley DL, Grunkemeier GL, Teply JF, Abbruzzese PA, Savis JS, Khonsari S, Starr A. Coronary bypass operation following acute complicated myocardial infarction. J Thorac Cardiovasc Surg 1983;85:485-91. Williams DB, Ivey TD, Bailey WW, Irey SJ, Rideout JT, Stewart D. Postinfarction angina: results of early revascularization. J Am Co11 Cardiol 1983;2:859-64. Baumgartner WA, Borkon AM, Zibulewsky J, Watkins L, Gardner TJ, Bulkley BH, Achuff SC, Baughman KL, Trail1 TA, Gott VL, Reitz RA. Operative intervention for postinfarction angina. Ann Thorac Surg 1984;38:265-7.
Catecholamines Pathophysiologic Pallab
K. Ganguly,
Manitoba,
From the Department of Anatomy, Division of Cardiovascular Sciences,St. General
Hospital
Research
Centre,
University
of Manitoba.
This work was supported Dr. Ganguly is a scholar
by a grant from the Manitoba Heart of the Canadian Heart Foundation.
Received
May
for publication
9, 1989;
accepted
June
Foundation.
15, 1989.
Reprint requests: Pallab K. Ganguly, MD, Division of Cardiovascular ences, St. Boniface General Hospital Research Centre, 351 Tache Winnipeg, Manitoba, Canada R2H 2A6.
4/l/14654
868
disorders:
Canada
Over the last three decades, numerous investigators in a multitude of clinical as well as experimental studies have contributed substantially to our understanding of the functional status of the sympathetic
Boniface
83. Gertler JP, Elefteriades JA, Kopf GS, Hashim SW, Hammond GL. Geha AS. Predictors of outcome in early revascularization after acute myocardial infarction. Am J Surg 1985;149:441-4. 84. Singh AK, Rivera R, Cooper GN, Karlson KE. Early myocardial revascularization for post infarction angina: results and longterm follow-up. J Am Co11Cardiol 1985;6:1121-5. 85. Brower RA, Fioretti P, Simoons ML, Haalebos M, Rulf ENR, Hugenholtz PG. Surgical versus non surgical management of patients soon after acute myocardial infarction. Br Heart .I 1985;54:460-5. 86. Breyer RH, Engelman RM, Rousou JA, Lemeshow S. Postinfarction angina: an expanding subset of patients undergoing bypass surgery. J Thorac Cardiovasc Surg 1985;90:532-40. 87. Jones RN, Pifarre R, Sullivan HJ, Montoga A, Bakhos M, Grieco JG, Foy BK, Wyatt J. Early myocardial revascularization for postinfarction angina. Ann Thorac Surg 1987;44:15962. 88. Stuart RS, Baumgartner WA, Soule L, Borkon AM, Gardner TJ, Gott VL, Watkins SL, Reitz BA. Predictors of perioperative mortality in patients with unstable postinfarction angina. Circulation 1988;78(suppl 1):1-163-I-165. 89. Russell RO, Maraski RE, Kouchoukos NT, et al. Unstable angina pectoris: National Cooperative study group to compare medical and surgical therap:l. II. In hospital experience and initial follow-up results in patients with one, two and three vessel disease. Am J Cardiol 1978;42:839-49. 90. Scott SM, Luchi RJ, Deupree RH. Veterans Administration Cooperative study for treatment of patients with unstable angina: results in patients with abnormal left ventricular function. Circulation 1988;78(suppl 1):1-113-I-121. 91. Simpson JB, Robertson GC, Selmon MR. Percutaneous coronary atherectomy [Abstract]. Circulation 1988;78(suppl II):II-82. 92. Spears JR, Reye VP, VP, James LM, Sinofsky EL. Laser balloon angioplasty-initial clinical percutaneous coronary results [Abstract]. Circulation 1988;78(suppl II):II-296.
and cardiovascular considerations
MD. Winnipeg,
October 1989 Heart Journal
SciAve.,
system in cardiovascular diseases. Today, virtually many if not all common complications associated with cardiovascular diseases have been correlated at one point or another with the sympathetic neural activity. The most compelling evidence of the involvement of catecholamines is the demonstration that many drugs therapeutically useful in treatment also affect the sympathetic nervous system at various sites, modifying the synthesis, release, uptake, and storage of catecholamines or acting directly on the adrenergic receptors. Although it is not surprising that the sympathetic system is altered as cardiac function deteriorates under a wide variety of situa-
Volume
110
Number
4
tions, it now appears that this system may overreact if activated for a prolonged period of time and this overreaction may cause detrimental cardiovascular effects. The purpose of this article is to summarize the functional status of the sympathetic system in some cardiologic disease states and to highlight a few aspects of sympathetic neural activity that I believe are important in the overall understanding of the pathophysiologic process. At the outset, the objectives of such an approach must be clearly understood. First, the recent introduction of sensitive, specific techniques for measuring catecholamines and their oxidative products has allowed definite testing of the hypothesis about the involvement of sympathetic activity in cardiovascular diseases. Second, in order to understand the pathophysiologic implications of catecholamines in the disease process, it is perhaps important to evaluate critically the existing data in this field-those that support the concept as well as those data that are controversial. Finally, while there is compelling evidence that the sympathetic nervous system is involved in many cardiovascular disorders, the role of sympathetic activity in determining survival in cardiac patients is less certain. Thus attempts to delineate the factors derived from increased sympathetic activity are needed, and it is with such a physiologically based approach to the investigation of the involvement of catecholamines in cardiovascular diseases that this article will be concerned. There are now several reports that suggest that plasma concentrations of norepinephrine reflect the activity of the sympathetic nervous system.ll 2 Plasma norepinephrine levels increase after myocardial infarction.39 4 While the role played by the considerable stress response due to the chest pain, the transfer to the hospital, and confrontation with the conditions of intensive care has been implicated in this disease process,l the extent of the increase in both the norepinephrine and epinephrine level is now known to be related to the severity of the infarction and to the development of arrhythmias.5 The association of higher epinephrine concentrations with increasing severity of arrhythmias, as well as the higher norepinephrine levels in those patients with ventricular fibrillation, suggests that sympathetic activity plays an important role in a vicious circle that increases myocardial irritability and damage. In patients with congestive heart failure, there is also an elevation of blood norepinephrine concentrations at rest that correlates with the severity of the congestive failure.6s7 While it has been suggested that plasma norepinephrine may act as a support mechanism in the failing heart, evidence from several groups has shown that cardiac P-adrenergic receptor values are
Adrenergic
activity in cardiac disease
869
reduced in congestive heart failure, either as a result of receptor desensitization or downregulation. The interrelationship between sympathetic neural activity, plasma catecholamines, and essential hypertension, on the other hand, has been a controversial topic. There are reports that suggest that elevated plasma norepinephrine levels may characterize an early stage in the development of essential hypertension in some patients.g However, a view that peripheral sympathetic nervous system hyperactivity is directly related in a cause-and-effect manner to essential hypertension in general appears inaccurate. In fact, changes in plasma norepinephrine in essential hypertension may be a secondary phenomenon unrelated to etiology. Insufficient data are available to make strong inferences about sympathetic activity in other forms of hypertension. Whatever the mechanisms may be, it is apparent that the heart, compensates for an increased work load by enlarging its muscle mass, and cardiac hypertrophy is a common manifestation in hypertension. An increased sympathetic activity has also been implicated by various investigators in this process.lOp l1 Similarly, studies with both diabetic patients and diabetic animals have indicated the possibility of an altered activity of the sympathetic nervous system.12t l3 The plasma level of norepinephrine increases in diabetes12y l4 and is associated with functional, biochemical, and ultrastructural alterations in cardiac cells.13, l5 It may be pointed out that when the plasma norepinephrine level has been used as an index of sympathetic neural activity, norepinephrine levels in a variety of cardiologic disease states have been described in several reports. However, the level of circulating norepinephrine as a reflection of sympathetic tone at a given stage of disease should be viewed with caution.2 Plasma norepinephrine levels seen in some patients result not from increased sympathetic outflow but from decreased clearance of norepinephrine.2 This is further complicated by the fact that there is no ideal method for completely stress-free blood collection, and thus stress may obscure any interpretation. Unfortunately, the relation between circulating catecholamine levels and the activity of the sympathetic system is obscured in the clinical situation by the lack of detailed information regarding the myocardial norepinephrine concentration, its uptake, turnover, and metabolism in various cardiovascular diseases. The norepinephrine content. of the human myocardium has been studied biochemically by several authors.16-18 Histochemical studies of the cardiac adrenergic nerve network have also been reported.lg Since there are difficulties in obtaining myocardial biopsies from healthy subjects, it is not yet known
870
Ganguly
what the exact level of myocardial norepinephrine in normal subjects is. In patients with heart failure, the myocardial norepinephrine concentration is considerably reduced (relative to other disease states).“” There is biochemical, histochemical, and other experimental evidence suggesting that the reduction of cardiac norepinephrine concentrations in heart failure is only partially explained by simple dilution of adrenergic nerve endings in the hypertrophied muscle mass, and that there is a true depletion of norepinephrine in the myocardium.20 A recent report,7 however, indicates heterogenous myocardial catecholamine concentrations in patients with congestive heart failure. A significant correlation existed between the norepinephrine concentration and the tyrosine hydroxylase and dopamine P-hydroxylase; the activities of these catecholamine synthetic enzymes were also found to be 10w.~l Furthermore, it appears that, in addition to a defect in norepinephrine synthesis, neuronal binding and uptake of catecholamines may be impaired in heart failure.22 There is also experimental evidence that an extremely high and sustained sympathetic activity inherent in heart failure is associated with very high cardiac norepinephrine turnover. 23 On the other hand, in patients with symptomatic ischemic heart disease, a relatively high myocardial norepinephrine level is observed.23 This is accompanied by increased activities of tyrosine hydroxylase and dopamine &hydroxylase.2” Accumulation of catecholamines into the ischemic myocardium may result in several adverse electrophysiologic, metabolic, vascular, and other processes in the heart. Isoproterenol-induced myocytolysis in heart muscle is associated with an increased turnover of norepinephrine as a result of increased release of a physiologically active neurotransmitter.24 In experimental hypertension, a decreased concentration of norepinephrine in the heart has been repeatedly demonstrated, and some authors have also shown diminished total content. 25 A study of norepinephrine turnover in the heart of animals subjected to renal infarction revealed that normotensive and hypertensive animals behaved as a single population.26 The turnover rate was not significantly different from that of the control animals. Using different model of hypertension, other investigators,26 however, have shown decreased norepinephrine concentration and increased norepinephrine turnover in the heart. There are even reports that suggest an increased turnover and unchanged norepinephrine concentration. As stated earlier, at present most of the studies indicate the presence of significant changes in cardiac norepinephrine in hypertension. Furthermore, norepinephrine kinetics in patients with essential
American
October 1989 Heart Journal
hypertension27 suggest that sympathetic activity is indeed increased in this disease state. Although changes in cardiac norepinephrine synthesis, storage, and metabolism have been reported earlier in a wide variety of pathologic conditions, the ability of the heart to handle norepinephrine in diabetes has been a subject of recent interest. It has been shown that diabetes is associated with an increased cardiac norepinephrine concentration and rate of norepinephrine turnover. I3 It is possible that these findings could be the result of increased synthesis of norepinephrine within the sympathetic nerve terminals or increased uptake across the neuronal membrane. Moreover, a defect in the metabolism, utilization, and release from the storage granules within the nerve terminal may also initiate changes in norepinephrine turnover and the plasma norepinephrine level such as are observed in the diabetic heart.14 From the foregoing discussion, it is apparent that the involvement of the sympathetic system is an integral part in many common cardiovascular diseases. The question now arises as to what initiates increased peripheral sympathetic tone? Several reports now suggest that the central catecholaminergic system may be responsible for the increased peripheral sympathetic nerve function in many cardiovascular disease processes. In the last decade, a number of catecholamine-containing neurons have been identified within the central nervous system that are localized in or project into cardiovascular centers within the brain or spinal cord and are involved in cardiovascular regulation.28, 2g Furthermore, central and peripheral catecholamines are frequently colocalized within neurons with peptidergic substances.30 Accordingly, these peptides have been increasingly studied for their possible role as neuromodulator, both in the central nervous system and in the periphery. This research holds great promise for the development of new pharmacologic drugs for the treatment of cardiovascular abnormalities in a wide variety of disease situations. Because of the profound metabolic effects of the individual disease condition, one can not overlook other etiologic factors that are equally important in the overall trigger mechanisms for higher sympathetic tone. Accordingly, more experiments are needed before we can arrive at any meaningful conclusion. Is increased sympathetic tone with its attendant high plasma norepinephrine concentration necessarily detrimental to cardiac tissue? Is increased sympathetic activity a cause or an effect? Does a common mechanism explain the diverse complications in cardiovascular diseases? Although many more experiments are needed before we can answer these ques-
Volume Number
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tions, it is perhaps true that stressful conditions for a prolonged period are invariably associated with high levels of circulating catecholamines and heart disease. Numerous investigators have contributed substantially to our understanding of the biochemical basis for the cardiotoxic action of catecholamines. One important aspect in this regard is the involvement of abnormal movements of Ca2+, which are required to activate biochemical processes during cardiac contraction.31 The occurrence of intracellular Ca2+ overload due to the defects of cardiac subcellular membranes initiates a variety of events including excessive utilization of high-energy phosphates and alterations in cellular integrity, leading to cell death. A new hypothesis has been put forward concerning the pathomechanism of catecholamine-induced myocardial injury, where adrenochrome, one of the oxidation products of catecholamines and free radicals, is regarded as a possible candidate for cardiotoxicity during the presence of excess levels of catecholamines in the circulation.32-34 The accumulation of oxidation products of catecholamines in the myocardium could directly or indirectly-by acting by themselves or in conjunction with other effects of catecholamines-initiate processes leading to myocardial damage. In fact, adrenochrome has been shown to impair the contractile function of the heart, and this deleterious action is clearly a dose- and time-dependent phenomenon.33 The toxic influence of adrenochrome on the myocardium and its modification by various cationic and pharmacologic agents support the participation of this oxidation product in the pathogenesis of catecholamine-induced cardiotoxicity. It has been proposed that in certain stressful conditions, monoamine oxidase and catechol-0-methyltransferase, which are normally concerned with metabolism of catecholamines, may either become saturated or defective, and thus catecholamines are available under in vivo situations for oxidation to adrenochrome and free radicals. This in turn produces coronary spasm,35 arrhythmias,36 ultrastructural damage,33 and ventricular dysfunction.32 Therefore, in order to establish the exact role of adrenochrome in the pathogenesis of catecholamine injury, a precise method for the demonstration of adrenochrome in vivo is required. Adrenochrome disappears upon its exposure to blood, an observation that indicates that blood cells may be involved in the oxidation of adrenochrome to other metabolites such as adrenolutin.37 By using the reverse phase of highperformance liquid chromatography with mobile phases composed of simple acids, an assay technique has been developed for the measurement of
Adrenergic
activity in cardiac disease
87 1
adrenolutin.37 In view of in vitro and in vivo observations regarding the formation of adrenolutin from epinephrine, it is possible that the level of adrenolutin in plasma may reflect the extent of oxidation of circulating catecholamines. It may be pointed out that adrenolutin is present in the plasma of many species including humans, and high levels of plasma adrenolutin may suggest the presence of an efficient mechanism for the oxidation of catecholamines under in vivo conditions. The plasma level of adrenolutin in various cardiovascular diseases, however, remains to be investigated. A selective increase in other forms of neurotransmitter turnover within the myocardium can also evoke a change in cellular redox status. Because the turnover of dopamine by monoamine oxidase is associated with the formation of a cellular oxidant, namely, hydrogen peroxide, increased neuronal activity could in fact be associated with an oxidative stress.38 Increased generation of hydrogen peroxide results in either tissue damage or overt cellular destruction. Although some efforts have been made to understand the status of dopamine level and dopaminergic receptors in various cardiovascular diseases,3g! 4o studies on dopamine turnover have not been done carefully and therefore this possibility remains to be explored. In conclusion, several cardiovascular diseases are associated with increased sympathetic activity and at present one may reasonably hypothesize participation of the sympathetic nervous system in the pathophysiologic process. A persistent oxidative stress resulting from increased sympathetic tone, coupled with other etiologic factors, may produce significant abnormalities in the heart. A therapeutic trial of antioxidants to slow the progression of cardiac abnormalities may be considered in the future. REFERENCES
1. Goldstein DS. Plasma norepinephrine as an indicator of sympathetic neural activity in clinical cardiology. Am J Cardiol 1981;48:1147-54. 2. Goldstein DS. Plasma catecholamines in clinical studies of cardiovascular diseases. Acta Physiol Stand 1984;527 (Suppl):39-41. 3. Gazes PC, Richardson JA, Woods EF. Plasma catecholamine concentrations in myocardial infarction and angina pectoris. Circulation 1959;19:657-61. 4. Videbaek J, Cristensen NJ, Sterndorff B. Serial determination of plasma catecholamines in myocardial infarction. Circulation 1972;46:846-55. 5. Bertel 0, Biihler FR, Baitsch G, Ritz R, Burkart F. Plasma adrenaline and noradrenaline in patients with acute myocardial infarction. Relationship to ventricular arrhythmias of varying severity. Chest 1982;82:64-8. 6. Thomas JA, Marks BH. Plasma norepinephrine in congestive heart failure. Am J Cardiol 1978;41:233-43. 7. Pierpont GL, Francis GS, DeMaster EG, Olivari MT, Ring WS, Goldenberg IF, Reynolds S, Cohn JN. Heterogenous my-
872
8.
9. 10. 11. 12. 13. 14. 15.
16. 17. 18. 19.
20. 21.
22. 23. 24.
Gun&
ocardial catecholamine concentrations in patients with congestive heart failure. Am J Cardiol 1987;60:316-21. Bristow MR, Ginsberg R, Minobe W, Cubiccotti RS, Sagemen WS, Lurie K, Billingham ME, Harrison DC, Stinson EB. Decreased catecholamine sensitivity and beta-adrenergic receptor density in failing human heart. N Engl J Med 1982;307:20511. Goldstein DS. Plasma norepinephrine in essential hypertension: a study of the studies. Hypertension 1981;3:48-52. Ganguly PK, Lee SL, Beamish RE, Dhalla NS. Altered sympathetic system and adrenoceptors during the development of cardiac hypertrophy. AM HEART J 1989 (In press) Rossi MA, Carillo SV. Does norepinephrine play a central causative role in the process of cardiac hypertrophy? AM HEART J 1985;109:622-4. Christensen NJ. Plasma norepinephrine and epinephrine in untreated diabetics, during fasting and after insulin administration. Diabetes 1974;23:1-8. Ganguly PK, DhaIla KS, Innes IR, Beamish RE, Dhalla NS. Altered norepinephrine turnover and metabolism in diabetic cardiomyopathy.-Circ Res 1986;59:684-93. Ganeulv PK. Beamish RE. Dhalla KS. Innes IR. Dhalla NS. Norepinephrine storage, distribution and release in diabetic cardiomyopathy. Am J Physiol 1987;252:E734-9. Ganguly PK, Dhalla KS, Beamish RE, Innes IR, Dhalla NS. Involvement of catecholamines in the development of diabetic cardiomvonathv. In: Dhalla NS. Sinaal PK. Beamish RE. eds. Pathophysiology of heart disease. Boston: Martinus Nijhoff Publishing, 1987:237-48. Chidsey CA, Braunwald E, Morrow AG. Catecholamine excretion of cardiac stores of norepinephrine in congestive heart. failure. AM HEART J 1965;39:442-50. De Quattro V, Nagatsu T, Mendez A, Verska J. Determinants of cardiac noradrenaline depletion in human congestive failure. Cardiovasc Res 1973;7:344-8. Petch MC, Nayler WG. Concentration of catecholamines in human cardiac muscle. Br Heart J 1979;41:340-4. Penttila 0, Kyiisola K, Partanen S, Merikallio E, Siltanen P. Studies of auricular catecholamines by fluorescence histochemistry in various heart diseases of man. Virchows Arch A 1977;373:279-84. Chidsey CA, Braunwald E, Morrow AG, Mason DT. Myocardial norepinephrine concentration in man: effects of reserpine and congestive heart failure. N Engl J Med 1963;269:653-8. Siltanen P, Penttila 0, Merikallio E, Kyiisola K, Klinge E, Pispa d. Myocardial catecholamines and their biosynthetic enzymes in various human heart diseases. Acta Med Stand 1982;66O(Suppl):24-33. Petch MC, Nayler WG. Uptake of catecholamines by human cardiac muscle in vitro. Br Heart J 1979;41:336-9. Sole MJ, Lo CM, Laird CW, Sonnenblick EH, Wurtman RJ. Norepinephrine turnover in the heart and spleen of the cardiomyopathic Syrian hamster. Circ Res 1975;37:855-62. Mueller RA, Thoenen H. Cardiac catecholamine synthesis turnover and metabolism with isoproterenol-induced myocytolysis. Cardiovasc Res 1971;5:364-70.
American
October IQ89 Heart Journal
25. Krakoff LR, de Champlain J, Axelrod J. Abnormal storage of norepinephrine in experimental hypertension in the rat. Circ Res 1967;21:583-91. 26 Kurnjek ML, Basso N, Taquini AC. Norepinephrine turnover in the heart and blood vessels of rats subjected to bilateral renal infarction. Arch Int Phvsiol Biochim 1984:92:53-63. 27 Esler M, Jackman G, Bobik A, Leonard P, Kelleher D, Skews H, Jennings G, Korner P. Norepinephrine kinetics in essential hypertension. Defective neuronal uptake of norepinephrine in some patients. Hypertension 1981;3:149-56. 28. Saper CB, Reis DJ, Joh T. Medullary catecholamine input to the anteroventral third ventricular cardiovascular regulatory region in the rat. Neurosci Lett 1983;42:285-91. 29. Sawchenko PE, Swanson LW. The organization of noradrenergic pathways from the brainstem to the paraventricular and supra optic nuclei in the rat. Brain Res Rev 1982;4:275-325. 30. Okamura H, Murakami S, Yanaihara N, Ibada Y. Coexistance of catecholamines and methionine enkephaline Arg 6 Gly 7 Leu 8 in neurons of the rats ventrolateral medulla oblongata. Application of combined peptide immunohistochemistry and histofhrorescent method in the same vibratome section. Histochemistry 1989;91:31-4. 31. Rona G. Catecholamine cardiotoxicity. J Mol Cell Cardiol 1985;17:291-306. 32. Yates JC, Beamish RE, Dhalla NS. Ventricular dysfunction and necrosis produced by adrenochrome metabolite of epinephrine: relation to pathogenesis of catecholamine cardiomyopathy. AM HEART J 1981;102:210-21. 33. Singal PK, Dhillon DS, Beamish RE, Kapur N, Dhalla NS. Myocardial cell damage and cardiovascular changes due to IV. infusion of adrenochrome in rats. Br J Exp Path01 1982;63:167 76. 34. Ganguly PK, Beamish RE, Dhalla NS. Catecholamine cardiotoxicity in pheochromocytoma. AM HEART J 1989;117:1399400. 35. Karmazyn M, Beamish RE, Fliegel L, Dhalla NS. Adrenochrome-induced coronary artery constriction in the rat heart. J Pharmacol Exp Ther 1981;219:225-30. 36. Beamish RE. Dhillon KS. Sineal PK. Dhalla NS. Protective effect of sulfinpyrazone against catecholamine metabolite adrenochrome-induced arrhythmias. AM HEART J 1981; 102:149-52. 37. Dhalla KS, Ganguly PK, Rupp H, Beamish RE, Dhalla NS. Measurement of adrenolutin as an oxidation product of catecholamines in plasma. Mol Cell Biochem 1989;87:85-92. 38. Spina MB, Cohen G. Dopamine turnover and glutathione oxidation: implications for Parkinson’s disease. Proc Nat1 Acad Sci USA 1989;86:1398-400. 39. Sole MJ, Helke CJ, Jacobowitz DM. Increased dopamine in the failing hamster heart: transvesicular transport of dopamine limits the rate of norepinephrine systhesis. Am J Cardiol 1982;49:1682-90. 40. Bercowitz BA, Ohlstein EH. Cardiovascular dopamine receptors: recent advances in agonists and antagonists of the DAlreceptor. d Cardiovasc Pharmacol 1984;6:S559-63.
74.
75.
76.
77.
78.
79. 80.
81. 82.
American
Gardner TJ. Unstable angina pectoris. Factors influencing operative risk. Ann Surg 1980;19:745. Rankin JS, Newton JR, Califf RM, Jones RH, Wechsler AS, Oldham HN, Wolfe WG, Lowe JE. Clinical characteristics and current management of medically refractory unstable angina. Ann Surg 1984;200:457-64. Rahimtoola SH, Nunley D, Grunkemeier G, Tepley J, Lambert L, Starr A. Ten year survival after coronary bypass surgery for unstable angina. N Engl J Med 1983;308:676-81. Cohn LH, O’Neill A, Collins JJ. Surgical treatment of unstable angina up to 1984. In: Hugenholtz PG, Goldman BS, eds. Unstable angina-current concepts and management. New York: Stuttgart: Schattauer, 1985:279-86. Goldman HE, Weisel RD, Christakis G, Katz A, Scully HE, Mickleborough LM, Baird RJ. Predictors of outcome after coronary artery bypass graft surgery for stable and unstable angina pectoris. In: Hugenholtz PG, Goldman BS, eds. Unstable angina-current concepts and management. New York Stuttgart: Schattauer, 1985319-29. McCormick JR, Schick EC, MC Gabe CH, Kronmal RA, Ryan TJ. Determinants of operative mortality and longterm survival in patients with unstable angina. J Thorac Cardiovasc Surg 1985;89:683-8. Luchi RJ, Scott SM, Deupree RH, et al. Comparison of medical and surgical treatment for unstable angina. N Engl J Med 1987;316:977-84. Nunley DL, Grunkemeier GL, Teply JF, Abbruzzese PA, Savis JS, Khonsari S, Starr A. Coronary bypass operation following acute complicated myocardial infarction. J Thorac Cardiovasc Surg 1983;85:485-91. Williams DB, Ivey TD, Bailey WW, Irey SJ, Rideout JT, Stewart D. Postinfarction angina: results of early revascularization. J Am Co11 Cardiol 1983;2:859-64. Baumgartner WA, Borkon AM, Zibulewsky J, Watkins L, Gardner TJ, Bulkley BH, Achuff SC, Baughman KL, Trail1 TA, Gott VL, Reitz RA. Operative intervention for postinfarction angina. Ann Thorac Surg 1984;38:265-7.
Catecholamines Pathophysiologic Pallab
K. Ganguly,
Manitoba,
From the Department of Anatomy, Division of Cardiovascular Sciences,St. General
Hospital
Research
Centre,
University
of Manitoba.
This work was supported Dr. Ganguly is a scholar
by a grant from the Manitoba Heart of the Canadian Heart Foundation.
Received
May
for publication
9, 1989;
accepted
June
Foundation.
15, 1989.
Reprint requests: Pallab K. Ganguly, MD, Division of Cardiovascular ences, St. Boniface General Hospital Research Centre, 351 Tache Winnipeg, Manitoba, Canada R2H 2A6.
4/l/14654
868
disorders:
Canada
Over the last three decades, numerous investigators in a multitude of clinical as well as experimental studies have contributed substantially to our understanding of the functional status of the sympathetic
Boniface
83. Gertler JP, Elefteriades JA, Kopf GS, Hashim SW, Hammond GL. Geha AS. Predictors of outcome in early revascularization after acute myocardial infarction. Am J Surg 1985;149:441-4. 84. Singh AK, Rivera R, Cooper GN, Karlson KE. Early myocardial revascularization for post infarction angina: results and longterm follow-up. J Am Co11Cardiol 1985;6:1121-5. 85. Brower RA, Fioretti P, Simoons ML, Haalebos M, Rulf ENR, Hugenholtz PG. Surgical versus non surgical management of patients soon after acute myocardial infarction. Br Heart .I 1985;54:460-5. 86. Breyer RH, Engelman RM, Rousou JA, Lemeshow S. Postinfarction angina: an expanding subset of patients undergoing bypass surgery. J Thorac Cardiovasc Surg 1985;90:532-40. 87. Jones RN, Pifarre R, Sullivan HJ, Montoga A, Bakhos M, Grieco JG, Foy BK, Wyatt J. Early myocardial revascularization for postinfarction angina. Ann Thorac Surg 1987;44:15962. 88. Stuart RS, Baumgartner WA, Soule L, Borkon AM, Gardner TJ, Gott VL, Watkins SL, Reitz BA. Predictors of perioperative mortality in patients with unstable postinfarction angina. Circulation 1988;78(suppl 1):1-163-I-165. 89. Russell RO, Maraski RE, Kouchoukos NT, et al. Unstable angina pectoris: National Cooperative study group to compare medical and surgical therap:l. II. In hospital experience and initial follow-up results in patients with one, two and three vessel disease. Am J Cardiol 1978;42:839-49. 90. Scott SM, Luchi RJ, Deupree RH. Veterans Administration Cooperative study for treatment of patients with unstable angina: results in patients with abnormal left ventricular function. Circulation 1988;78(suppl 1):1-113-I-121. 91. Simpson JB, Robertson GC, Selmon MR. Percutaneous coronary atherectomy [Abstract]. Circulation 1988;78(suppl II):II-82. 92. Spears JR, Reye VP, VP, James LM, Sinofsky EL. Laser balloon angioplasty-initial clinical percutaneous coronary results [Abstract]. Circulation 1988;78(suppl II):II-296.
and cardiovascular considerations
MD. Winnipeg,
October 1989 Heart Journal
SciAve.,
system in cardiovascular diseases. Today, virtually many if not all common complications associated with cardiovascular diseases have been correlated at one point or another with the sympathetic neural activity. The most compelling evidence of the involvement of catecholamines is the demonstration that many drugs therapeutically useful in treatment also affect the sympathetic nervous system at various sites, modifying the synthesis, release, uptake, and storage of catecholamines or acting directly on the adrenergic receptors. Although it is not surprising that the sympathetic system is altered as cardiac function deteriorates under a wide variety of situa-
Volume
110
Number
4
tions, it now appears that this system may overreact if activated for a prolonged period of time and this overreaction may cause detrimental cardiovascular effects. The purpose of this article is to summarize the functional status of the sympathetic system in some cardiologic disease states and to highlight a few aspects of sympathetic neural activity that I believe are important in the overall understanding of the pathophysiologic process. At the outset, the objectives of such an approach must be clearly understood. First, the recent introduction of sensitive, specific techniques for measuring catecholamines and their oxidative products has allowed definite testing of the hypothesis about the involvement of sympathetic activity in cardiovascular diseases. Second, in order to understand the pathophysiologic implications of catecholamines in the disease process, it is perhaps important to evaluate critically the existing data in this field-those that support the concept as well as those data that are controversial. Finally, while there is compelling evidence that the sympathetic nervous system is involved in many cardiovascular disorders, the role of sympathetic activity in determining survival in cardiac patients is less certain. Thus attempts to delineate the factors derived from increased sympathetic activity are needed, and it is with such a physiologically based approach to the investigation of the involvement of catecholamines in cardiovascular diseases that this article will be concerned. There are now several reports that suggest that plasma concentrations of norepinephrine reflect the activity of the sympathetic nervous system.ll 2 Plasma norepinephrine levels increase after myocardial infarction.39 4 While the role played by the considerable stress response due to the chest pain, the transfer to the hospital, and confrontation with the conditions of intensive care has been implicated in this disease process,l the extent of the increase in both the norepinephrine and epinephrine level is now known to be related to the severity of the infarction and to the development of arrhythmias.5 The association of higher epinephrine concentrations with increasing severity of arrhythmias, as well as the higher norepinephrine levels in those patients with ventricular fibrillation, suggests that sympathetic activity plays an important role in a vicious circle that increases myocardial irritability and damage. In patients with congestive heart failure, there is also an elevation of blood norepinephrine concentrations at rest that correlates with the severity of the congestive failure.6s7 While it has been suggested that plasma norepinephrine may act as a support mechanism in the failing heart, evidence from several groups has shown that cardiac P-adrenergic receptor values are
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reduced in congestive heart failure, either as a result of receptor desensitization or downregulation. The interrelationship between sympathetic neural activity, plasma catecholamines, and essential hypertension, on the other hand, has been a controversial topic. There are reports that suggest that elevated plasma norepinephrine levels may characterize an early stage in the development of essential hypertension in some patients.g However, a view that peripheral sympathetic nervous system hyperactivity is directly related in a cause-and-effect manner to essential hypertension in general appears inaccurate. In fact, changes in plasma norepinephrine in essential hypertension may be a secondary phenomenon unrelated to etiology. Insufficient data are available to make strong inferences about sympathetic activity in other forms of hypertension. Whatever the mechanisms may be, it is apparent that the heart, compensates for an increased work load by enlarging its muscle mass, and cardiac hypertrophy is a common manifestation in hypertension. An increased sympathetic activity has also been implicated by various investigators in this process.lOp l1 Similarly, studies with both diabetic patients and diabetic animals have indicated the possibility of an altered activity of the sympathetic nervous system.12t l3 The plasma level of norepinephrine increases in diabetes12y l4 and is associated with functional, biochemical, and ultrastructural alterations in cardiac cells.13, l5 It may be pointed out that when the plasma norepinephrine level has been used as an index of sympathetic neural activity, norepinephrine levels in a variety of cardiologic disease states have been described in several reports. However, the level of circulating norepinephrine as a reflection of sympathetic tone at a given stage of disease should be viewed with caution.2 Plasma norepinephrine levels seen in some patients result not from increased sympathetic outflow but from decreased clearance of norepinephrine.2 This is further complicated by the fact that there is no ideal method for completely stress-free blood collection, and thus stress may obscure any interpretation. Unfortunately, the relation between circulating catecholamine levels and the activity of the sympathetic system is obscured in the clinical situation by the lack of detailed information regarding the myocardial norepinephrine concentration, its uptake, turnover, and metabolism in various cardiovascular diseases. The norepinephrine content. of the human myocardium has been studied biochemically by several authors.16-18 Histochemical studies of the cardiac adrenergic nerve network have also been reported.lg Since there are difficulties in obtaining myocardial biopsies from healthy subjects, it is not yet known
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what the exact level of myocardial norepinephrine in normal subjects is. In patients with heart failure, the myocardial norepinephrine concentration is considerably reduced (relative to other disease states).“” There is biochemical, histochemical, and other experimental evidence suggesting that the reduction of cardiac norepinephrine concentrations in heart failure is only partially explained by simple dilution of adrenergic nerve endings in the hypertrophied muscle mass, and that there is a true depletion of norepinephrine in the myocardium.20 A recent report,7 however, indicates heterogenous myocardial catecholamine concentrations in patients with congestive heart failure. A significant correlation existed between the norepinephrine concentration and the tyrosine hydroxylase and dopamine P-hydroxylase; the activities of these catecholamine synthetic enzymes were also found to be 10w.~l Furthermore, it appears that, in addition to a defect in norepinephrine synthesis, neuronal binding and uptake of catecholamines may be impaired in heart failure.22 There is also experimental evidence that an extremely high and sustained sympathetic activity inherent in heart failure is associated with very high cardiac norepinephrine turnover. 23 On the other hand, in patients with symptomatic ischemic heart disease, a relatively high myocardial norepinephrine level is observed.23 This is accompanied by increased activities of tyrosine hydroxylase and dopamine &hydroxylase.2” Accumulation of catecholamines into the ischemic myocardium may result in several adverse electrophysiologic, metabolic, vascular, and other processes in the heart. Isoproterenol-induced myocytolysis in heart muscle is associated with an increased turnover of norepinephrine as a result of increased release of a physiologically active neurotransmitter.24 In experimental hypertension, a decreased concentration of norepinephrine in the heart has been repeatedly demonstrated, and some authors have also shown diminished total content. 25 A study of norepinephrine turnover in the heart of animals subjected to renal infarction revealed that normotensive and hypertensive animals behaved as a single population.26 The turnover rate was not significantly different from that of the control animals. Using different model of hypertension, other investigators,26 however, have shown decreased norepinephrine concentration and increased norepinephrine turnover in the heart. There are even reports that suggest an increased turnover and unchanged norepinephrine concentration. As stated earlier, at present most of the studies indicate the presence of significant changes in cardiac norepinephrine in hypertension. Furthermore, norepinephrine kinetics in patients with essential
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hypertension27 suggest that sympathetic activity is indeed increased in this disease state. Although changes in cardiac norepinephrine synthesis, storage, and metabolism have been reported earlier in a wide variety of pathologic conditions, the ability of the heart to handle norepinephrine in diabetes has been a subject of recent interest. It has been shown that diabetes is associated with an increased cardiac norepinephrine concentration and rate of norepinephrine turnover. I3 It is possible that these findings could be the result of increased synthesis of norepinephrine within the sympathetic nerve terminals or increased uptake across the neuronal membrane. Moreover, a defect in the metabolism, utilization, and release from the storage granules within the nerve terminal may also initiate changes in norepinephrine turnover and the plasma norepinephrine level such as are observed in the diabetic heart.14 From the foregoing discussion, it is apparent that the involvement of the sympathetic system is an integral part in many common cardiovascular diseases. The question now arises as to what initiates increased peripheral sympathetic tone? Several reports now suggest that the central catecholaminergic system may be responsible for the increased peripheral sympathetic nerve function in many cardiovascular disease processes. In the last decade, a number of catecholamine-containing neurons have been identified within the central nervous system that are localized in or project into cardiovascular centers within the brain or spinal cord and are involved in cardiovascular regulation.28, 2g Furthermore, central and peripheral catecholamines are frequently colocalized within neurons with peptidergic substances.30 Accordingly, these peptides have been increasingly studied for their possible role as neuromodulator, both in the central nervous system and in the periphery. This research holds great promise for the development of new pharmacologic drugs for the treatment of cardiovascular abnormalities in a wide variety of disease situations. Because of the profound metabolic effects of the individual disease condition, one can not overlook other etiologic factors that are equally important in the overall trigger mechanisms for higher sympathetic tone. Accordingly, more experiments are needed before we can arrive at any meaningful conclusion. Is increased sympathetic tone with its attendant high plasma norepinephrine concentration necessarily detrimental to cardiac tissue? Is increased sympathetic activity a cause or an effect? Does a common mechanism explain the diverse complications in cardiovascular diseases? Although many more experiments are needed before we can answer these ques-
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tions, it is perhaps true that stressful conditions for a prolonged period are invariably associated with high levels of circulating catecholamines and heart disease. Numerous investigators have contributed substantially to our understanding of the biochemical basis for the cardiotoxic action of catecholamines. One important aspect in this regard is the involvement of abnormal movements of Ca2+, which are required to activate biochemical processes during cardiac contraction.31 The occurrence of intracellular Ca2+ overload due to the defects of cardiac subcellular membranes initiates a variety of events including excessive utilization of high-energy phosphates and alterations in cellular integrity, leading to cell death. A new hypothesis has been put forward concerning the pathomechanism of catecholamine-induced myocardial injury, where adrenochrome, one of the oxidation products of catecholamines and free radicals, is regarded as a possible candidate for cardiotoxicity during the presence of excess levels of catecholamines in the circulation.32-34 The accumulation of oxidation products of catecholamines in the myocardium could directly or indirectly-by acting by themselves or in conjunction with other effects of catecholamines-initiate processes leading to myocardial damage. In fact, adrenochrome has been shown to impair the contractile function of the heart, and this deleterious action is clearly a dose- and time-dependent phenomenon.33 The toxic influence of adrenochrome on the myocardium and its modification by various cationic and pharmacologic agents support the participation of this oxidation product in the pathogenesis of catecholamine-induced cardiotoxicity. It has been proposed that in certain stressful conditions, monoamine oxidase and catechol-0-methyltransferase, which are normally concerned with metabolism of catecholamines, may either become saturated or defective, and thus catecholamines are available under in vivo situations for oxidation to adrenochrome and free radicals. This in turn produces coronary spasm,35 arrhythmias,36 ultrastructural damage,33 and ventricular dysfunction.32 Therefore, in order to establish the exact role of adrenochrome in the pathogenesis of catecholamine injury, a precise method for the demonstration of adrenochrome in vivo is required. Adrenochrome disappears upon its exposure to blood, an observation that indicates that blood cells may be involved in the oxidation of adrenochrome to other metabolites such as adrenolutin.37 By using the reverse phase of highperformance liquid chromatography with mobile phases composed of simple acids, an assay technique has been developed for the measurement of
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adrenolutin.37 In view of in vitro and in vivo observations regarding the formation of adrenolutin from epinephrine, it is possible that the level of adrenolutin in plasma may reflect the extent of oxidation of circulating catecholamines. It may be pointed out that adrenolutin is present in the plasma of many species including humans, and high levels of plasma adrenolutin may suggest the presence of an efficient mechanism for the oxidation of catecholamines under in vivo conditions. The plasma level of adrenolutin in various cardiovascular diseases, however, remains to be investigated. A selective increase in other forms of neurotransmitter turnover within the myocardium can also evoke a change in cellular redox status. Because the turnover of dopamine by monoamine oxidase is associated with the formation of a cellular oxidant, namely, hydrogen peroxide, increased neuronal activity could in fact be associated with an oxidative stress.38 Increased generation of hydrogen peroxide results in either tissue damage or overt cellular destruction. Although some efforts have been made to understand the status of dopamine level and dopaminergic receptors in various cardiovascular diseases,3g! 4o studies on dopamine turnover have not been done carefully and therefore this possibility remains to be explored. In conclusion, several cardiovascular diseases are associated with increased sympathetic activity and at present one may reasonably hypothesize participation of the sympathetic nervous system in the pathophysiologic process. A persistent oxidative stress resulting from increased sympathetic tone, coupled with other etiologic factors, may produce significant abnormalities in the heart. A therapeutic trial of antioxidants to slow the progression of cardiac abnormalities may be considered in the future. REFERENCES
1. Goldstein DS. Plasma norepinephrine as an indicator of sympathetic neural activity in clinical cardiology. Am J Cardiol 1981;48:1147-54. 2. Goldstein DS. Plasma catecholamines in clinical studies of cardiovascular diseases. Acta Physiol Stand 1984;527 (Suppl):39-41. 3. Gazes PC, Richardson JA, Woods EF. Plasma catecholamine concentrations in myocardial infarction and angina pectoris. Circulation 1959;19:657-61. 4. Videbaek J, Cristensen NJ, Sterndorff B. Serial determination of plasma catecholamines in myocardial infarction. Circulation 1972;46:846-55. 5. Bertel 0, Biihler FR, Baitsch G, Ritz R, Burkart F. Plasma adrenaline and noradrenaline in patients with acute myocardial infarction. Relationship to ventricular arrhythmias of varying severity. Chest 1982;82:64-8. 6. Thomas JA, Marks BH. Plasma norepinephrine in congestive heart failure. Am J Cardiol 1978;41:233-43. 7. Pierpont GL, Francis GS, DeMaster EG, Olivari MT, Ring WS, Goldenberg IF, Reynolds S, Cohn JN. Heterogenous my-
872
8.
9. 10. 11. 12. 13. 14. 15.
16. 17. 18. 19.
20. 21.
22. 23. 24.
Gun&
ocardial catecholamine concentrations in patients with congestive heart failure. Am J Cardiol 1987;60:316-21. Bristow MR, Ginsberg R, Minobe W, Cubiccotti RS, Sagemen WS, Lurie K, Billingham ME, Harrison DC, Stinson EB. Decreased catecholamine sensitivity and beta-adrenergic receptor density in failing human heart. N Engl J Med 1982;307:20511. Goldstein DS. Plasma norepinephrine in essential hypertension: a study of the studies. Hypertension 1981;3:48-52. Ganguly PK, Lee SL, Beamish RE, Dhalla NS. Altered sympathetic system and adrenoceptors during the development of cardiac hypertrophy. AM HEART J 1989 (In press) Rossi MA, Carillo SV. Does norepinephrine play a central causative role in the process of cardiac hypertrophy? AM HEART J 1985;109:622-4. Christensen NJ. Plasma norepinephrine and epinephrine in untreated diabetics, during fasting and after insulin administration. Diabetes 1974;23:1-8. Ganguly PK, DhaIla KS, Innes IR, Beamish RE, Dhalla NS. Altered norepinephrine turnover and metabolism in diabetic cardiomyopathy.-Circ Res 1986;59:684-93. Ganeulv PK. Beamish RE. Dhalla KS. Innes IR. Dhalla NS. Norepinephrine storage, distribution and release in diabetic cardiomyopathy. Am J Physiol 1987;252:E734-9. Ganguly PK, Dhalla KS, Beamish RE, Innes IR, Dhalla NS. Involvement of catecholamines in the development of diabetic cardiomvonathv. In: Dhalla NS. Sinaal PK. Beamish RE. eds. Pathophysiology of heart disease. Boston: Martinus Nijhoff Publishing, 1987:237-48. Chidsey CA, Braunwald E, Morrow AG. Catecholamine excretion of cardiac stores of norepinephrine in congestive heart. failure. AM HEART J 1965;39:442-50. De Quattro V, Nagatsu T, Mendez A, Verska J. Determinants of cardiac noradrenaline depletion in human congestive failure. Cardiovasc Res 1973;7:344-8. Petch MC, Nayler WG. Concentration of catecholamines in human cardiac muscle. Br Heart J 1979;41:340-4. Penttila 0, Kyiisola K, Partanen S, Merikallio E, Siltanen P. Studies of auricular catecholamines by fluorescence histochemistry in various heart diseases of man. Virchows Arch A 1977;373:279-84. Chidsey CA, Braunwald E, Morrow AG, Mason DT. Myocardial norepinephrine concentration in man: effects of reserpine and congestive heart failure. N Engl J Med 1963;269:653-8. Siltanen P, Penttila 0, Merikallio E, Kyiisola K, Klinge E, Pispa d. Myocardial catecholamines and their biosynthetic enzymes in various human heart diseases. Acta Med Stand 1982;66O(Suppl):24-33. Petch MC, Nayler WG. Uptake of catecholamines by human cardiac muscle in vitro. Br Heart J 1979;41:336-9. Sole MJ, Lo CM, Laird CW, Sonnenblick EH, Wurtman RJ. Norepinephrine turnover in the heart and spleen of the cardiomyopathic Syrian hamster. Circ Res 1975;37:855-62. Mueller RA, Thoenen H. Cardiac catecholamine synthesis turnover and metabolism with isoproterenol-induced myocytolysis. Cardiovasc Res 1971;5:364-70.
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25. Krakoff LR, de Champlain J, Axelrod J. Abnormal storage of norepinephrine in experimental hypertension in the rat. Circ Res 1967;21:583-91. 26 Kurnjek ML, Basso N, Taquini AC. Norepinephrine turnover in the heart and blood vessels of rats subjected to bilateral renal infarction. Arch Int Phvsiol Biochim 1984:92:53-63. 27 Esler M, Jackman G, Bobik A, Leonard P, Kelleher D, Skews H, Jennings G, Korner P. Norepinephrine kinetics in essential hypertension. Defective neuronal uptake of norepinephrine in some patients. Hypertension 1981;3:149-56. 28. Saper CB, Reis DJ, Joh T. Medullary catecholamine input to the anteroventral third ventricular cardiovascular regulatory region in the rat. Neurosci Lett 1983;42:285-91. 29. Sawchenko PE, Swanson LW. The organization of noradrenergic pathways from the brainstem to the paraventricular and supra optic nuclei in the rat. Brain Res Rev 1982;4:275-325. 30. Okamura H, Murakami S, Yanaihara N, Ibada Y. Coexistance of catecholamines and methionine enkephaline Arg 6 Gly 7 Leu 8 in neurons of the rats ventrolateral medulla oblongata. Application of combined peptide immunohistochemistry and histofhrorescent method in the same vibratome section. Histochemistry 1989;91:31-4. 31. Rona G. Catecholamine cardiotoxicity. J Mol Cell Cardiol 1985;17:291-306. 32. Yates JC, Beamish RE, Dhalla NS. Ventricular dysfunction and necrosis produced by adrenochrome metabolite of epinephrine: relation to pathogenesis of catecholamine cardiomyopathy. AM HEART J 1981;102:210-21. 33. Singal PK, Dhillon DS, Beamish RE, Kapur N, Dhalla NS. Myocardial cell damage and cardiovascular changes due to IV. infusion of adrenochrome in rats. Br J Exp Path01 1982;63:167 76. 34. Ganguly PK, Beamish RE, Dhalla NS. Catecholamine cardiotoxicity in pheochromocytoma. AM HEART J 1989;117:1399400. 35. Karmazyn M, Beamish RE, Fliegel L, Dhalla NS. Adrenochrome-induced coronary artery constriction in the rat heart. J Pharmacol Exp Ther 1981;219:225-30. 36. Beamish RE. Dhillon KS. Sineal PK. Dhalla NS. Protective effect of sulfinpyrazone against catecholamine metabolite adrenochrome-induced arrhythmias. AM HEART J 1981; 102:149-52. 37. Dhalla KS, Ganguly PK, Rupp H, Beamish RE, Dhalla NS. Measurement of adrenolutin as an oxidation product of catecholamines in plasma. Mol Cell Biochem 1989;87:85-92. 38. Spina MB, Cohen G. Dopamine turnover and glutathione oxidation: implications for Parkinson’s disease. Proc Nat1 Acad Sci USA 1989;86:1398-400. 39. Sole MJ, Helke CJ, Jacobowitz DM. Increased dopamine in the failing hamster heart: transvesicular transport of dopamine limits the rate of norepinephrine systhesis. Am J Cardiol 1982;49:1682-90. 40. Bercowitz BA, Ohlstein EH. Cardiovascular dopamine receptors: recent advances in agonists and antagonists of the DAlreceptor. d Cardiovasc Pharmacol 1984;6:S559-63.