β-Adrenergic receptor changes during coronary artery bypass grafting

J THoRAc CARDIOVASC

SURG

1990;99:75-81

{3-Adrenergic receptor changes during coronary artery bypass grafting To evaluate whether the function of p-adrenergic receptors, essential to the biologic activity of catecholamines, is altered during coronary artery bypass grafting, we measured, in 16 patients undergoing myocardial revascularization, the density and the affinity of lymphocyte p-adrenergic receptors before anesthesia induction (control) and at the end of cardiopulmonary bypass. Variations in the density and affinity of p-adrenergic receptors were determined in vitro. Repeated determinations of plasma epinephrine and norepinephrine concentrations were also performed. Overall, no significant modification was observed in mean denSity and affinity of p-adrenergic receptors at the end of cardiopulmonary bypass when compared with control values. However, a significant decrease (P < 0.05) in affinity for isoproterenol was found in the six patients who had high catecholamine levels during cardiopulmonary bypass. In contrast, no significant modification of p-adrenoreceptor affinity for isoproterenol was observed in the 10 patients who did not have this degree of adrenergic activation. In addition, p-adrenoreceptor affinity for isoproterenol was decreased in the three patients in whom intraaortic balloon pumping was mandatory after discontinuation of cardiopulmonary bypass. We suggest that this decreased affinity of lymphocyte p-adrenergic receptors could be related, at least in part, to a sustained adrenergic activation occurring in some patients during cardiopulmonary bypass.

Jean Mantz; 'MD, Jean Marty, MD, Yves Pansard, MD, Danielle Henzel, Alain Loiseau, PhD, Marianne Pocidalo, MD, Jean Langlois, MD, and Jean-Marie Desmonts, MD, Paris, France

Since virtually all catecholamines (iJ-adrenergic agonists) exert their biologic action only by binding to specific receptor proteins on cell surfaces, alterations in the number (density) and sensitivity (affinity) of these receptors could affect outcome after cardiac operations. After binding, the final alteration in cellular metabolic events is mediated in part by cyclic adenosine monophosphate. The density and affinity of lymphocyte receptors (specifically the iJ-adrenergic receptors) have been shown to be similar to density and affinity of similar myocardial receptors, and lymphocytes are readily available for study.l-? In fact, Brodde and associates I recently established a close correlation between atrial and lymphocyte iJ-adrenergic receptor densities during cardiac operations. Rapid modFrom the Departments of Anesthesiology and Cardiovascular Surgery, INSERM U 82, and the Laboratory of Hematology, Hospital Bichat and Paris 7 University, Paris, France. Supported in part by a Contrat INSERM No 85-5007. Received for publication June 29,1988. Accepted for publication July 10, 1989. Address for reprints: ProMarty, Department of Anesthesiology, Hospital Bichat, 46 rue Henri Huchard, 75018-Paris, France.

12/1/15647

ifications in the number and the affinity of lymphocyte iJadrenergic receptors have been shown to occur during operations in response to variations in plasma catecholamine levels.t" Thus a sustained increase in circulating catecholamines (epinephrine and norepinephrine) results in both a decrease in the density of lymphocyte iJ-adrenergic receptors and a decreased affinity for iJ-adrenergic agonists. Variations in plasma catecholamine levels can also result in alteration in cyclic adenosine monophosphate production.t-" This becomes important, because it indicates similar changes in myocardial receptors and in vitro maximal developed contractile force of atrial fibers elicited by isoproterenol stimulation, which is closely correlated to the density of atrial iJ-adrenergic receptors. I Early biventricular dysfunction frequently develops during the first hours after discontinuation of cardiopulmonary bypass (CPB) during coronary artery bypass grafting.' Because iJ-adrenergic agonist agents like dobutamine are often used to facilitate the reversal of this post-CPB ventricular failure, it could be important to evaluate whether or not lymphocyte (and by inference myocardial) iJ-adrenergic receptor function is altered at the end of CPB. The present study was designed to assess the influence of high intraoperative catecholamine levels 75

The Journal of

76

Mantz et al.

Thoracic and Cardiovascular Surgery

Table I. CPR data Flow during CPS IL/minlm 2)

Rectal temp.

12 13 14 15 16

1.63 1.06 1.71 1.67 1.62 1.67 1.77 1.67 1.38 1.59 1.61 1.57 1.59 1.62 1.59 1.61

M±SEM

1.59 ± 0.04

Patient No. I

2 3 4 5 6 7 8 9 10 II

CPS duration

CPS 60 min

CPS before

63 55 60 62 61 60

21 19

30 37 35 35 33 40 30 37 36 35 35 35 35 25 28 32

23.2 ± 0.72

29.8 ± 2.75

(min}

CPS before

29.9 28.5 27.4 29.1 30.5 27.8 27.2 29.3 26.4 29.9 28.1 28.2 28.1 28.4 27.6 28.6

82 167 142 70 80 135 90 90 153 97 102 84 168 108 88 128

40 35 36 45 35 38 31 32 33 43 39 28 28 35 33 34

29 23 24 27 24 25 24 26 24 25 20 19 20

28.5 ± 0.2

ill ± 8

35.3 ± 1.17

rCJ

Plasma protein levels

Hematocrit 1%) CPS /5 min

22

/5 min

CPS 60 min

64 66 76 63 49 60 66 61 67

47 45 40 63 42 50 43 45 37 50 45 39 43 50 57 46

502 48 50 58 50 62 47 49 51 62 52 52 49 58 57 48

62.3 ± 1.4

45.3 ± 1.4

51.8 ± 1.2

64

CPS

M ± SEM, Mean ± standard error of the mean.

on j3-adrenergic receptor function by comparing the characteristics of lymphocyte j3-adrenergic receptors (density, affinity) between the end of CPB and control values obtained just before anesthesia induction in patients undergoing myocardial revascularization. Methods Patients. Sixteen patients (14 men and two women) scheduled for coronary artery bypass grafting gave informed consent to participate in the study. Institutional approval was obtained from the local human research committee of ethics. Five patients had previous myocardial infarction, and in four subjects there was a history of mild hypertension. All patients were receiving long-term oral {1-blocking drug therapy (acebutolol in 10, propranolol in four, atenolol in one, and metoprolol in one and were treated with calcium-entry blockers (diltiazem in seven and nifedipine in nine). Chronic oral therapy was continued until the morning of the operation. The last oral dose was given 3 hours before anesthesia induction and generally consisted of half a daily dose. Left ventricular ejection fraction was calculated from contrast left ventriculography. Patients with left or right ventricular failure, valvular heart disease, or arrhythmia were excluded from the study. Surgical procedure Anesthetic protocol. Premedication consisted of morphine hydrochloride (0.1 mg . kg -I) and scopolamine (0.5 mg) administered subcutaneously I V2 hour before the operation was begun .. Anesthesia was induced intravenously with high doses of fentanyl (50 f.Ig. kg- I at orotracheal intubation, 100 f.Ig . kg- I at sternotomy), flunitrazepam (10 f.Ig . kg-I), and pancuronium (0.1 mg . kg-I). Additional doses of fentanyl were further administered whenever heart rate or mean arterial pressure increased by more than 15% during the operation. Ventilation was maintained in 100% oxygen (Servo C venti-

lator, Siemens Elema AB, Solna, Sweden) and regularly checked by blood gas determination (arterial carbon dioxide tension between 33 and 38 torr). Blood was regularly sampled for determination of hematocrit and protein plasma levels. An indwelling radial artery catheter was inserted under local anesthesia before anesthesia induction for continuous monitoring of arterial blood pressure (systolic, diastolic, and mean). Pulmonary artery pressures (systolic, diastolic, and mean), pulmonary wedge pressure, and mean right atrial pressure were obtained from a Swan-Ganz catheter (Baxter Edwards Divisions, Irvine, Calif.) inserted via the right internal jugular vein before anesthesia induction. Cardiac index was derived from cardiac output measurements by the thermodilution method and systemic vascular resistances were calculated. No {1-adrenergic agonist or antagonist drug was used during the study period. The electrocardiogram was continuously monitored by the V5 derivation. CPB. The CPB circuit was primed with a 2300 ml volume that consisted of a mixture of fresh frozen plasma (1100 ml), sodium bicarbonate 0.16 mol/L (400 ml), Ringer's lactate (800 ml), calcium chloride (20 rnmol/L), and heparin (9000 IU). Additional heparin was injected approximately IS minutes before CPB was begun. The oxygenator was a Bentley-BOS 10 (buller) (Bentley Laboratories, Inc., Irvine, Calif.) After aortic crossclamping, cardioplegic solution was infused via the aortic root (St. Thomas' Hospital solution that consisted of700 to 1200 ml of cold potassium-enriched fluid); moderate hypothermia was induced (28° ± O.2°C rectal temperature), and nonpulsatile blood flow was adjusted to about 40 ml . kg-I. min· L. Pertinent CPB data are given in Table I. The a-adrenergic drugs phenylephrine and phentolamine were available if needed to maintain mean arterial pressure between 50 and 80 mm Hg. Assays {1-Adrenergic receptor binding studies. Two 80 ml blood samples were obtained for lymphocyte binding studies, first before anesthesia induction from the Swan-Ganz catheter and

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{3-Adrenergic receptors and coronary artery operations 7 7

Number 1

January 1990

Table II. Variations in density and affinity of lymphocyte {3-adrenergic receptor between anesthesia induction (control) and the end of CPB Control

Receptordensity 44.9 ± 2.7 (Bmax; fmoljmg) Affinity for 13.4 ± 2.7 antagonist (Kd; pmoljL) Affinity for 2599 ± 423 agonist (lC 50; nrnol/L)

End of CPS

Epinephrine p Value

4\.4 ± 4.1

>0.05

11.1 ± 0.8

>0.05

2729 ± 453

>0.05

Values are mean ± standard error of the mean. Bmax, ~-Adrenergic receptor density; Kd, dissociation constant; l'C 50, isoproterenol concentration able to remove 50% of radiolabeled 1251-iodocyanopindol from its receptors.

second from the oxygenator at the end of CPB, before the transfusion of any blood product, when the nasopharyngeal temperature was approximately 31 0 C. Heparinized whole blood was diluted with phosphate-buffered saline (pH = 7.4). Then lymphocytes were isolated on a FicolI*-Hypaquet density gradient by centrifugation (600 g for 2 minutes). The lymphocyte band was harvested by aspiration and resuspended in the same buffer. After two washings and additional centrifugations, the membrane preparation was obtained by a modification of the method ofFeldman and associates." Lymphocytes were resuspended in ice cold deionized water and broken up by ultrasonication for 10 seconds. Aliquots were then centrifuged at 40,000 g for 20 minutes at 4 0 C. The pellet was resuspended in 4 ml 0.9% NaCI with Tris 20 rnmol/L, MgCh 12.5 mmol/L, and ethylenediaminetetraacetate 1.5 mmol/L. Samples were frozen in liquid nitrogen (-70 0 C) until used for radioligand studies, which were performed within 2 weeks. Lymphocyte ,a-adrenergic receptor binding studies were performed on the prepared membranes by a method modified from that of Feldman and associates.> The assay was first extensively characterized: In fact, linearity with time and protein concentration, as well as stereoselectivity for (_)125 I-iodocyanopindolol (Amersham Corp., Arlington Heights, IIl., 2000 Ci] mmol/L) and (-)isoproterenol, was checked in preliminary experiments. In our assay conditions, equilibrium was reached after an incubation period of 60 to 70 minutes. An aliquot (0.1 ml) of membranes containing 20 to 50 f.Lg protein was incubated in a final volume of 250 f.Ll containing ascorbic acid 0.5mmol/L, bovine serum albumin 60 f.Lg/ml, phentolamine mesylate 0.03 mmol/L, Tris HCl 12 mmol/L (pH 7.4, 37 0 C), 0.054% NaCl, MgCh 7.5 mrnol/L, and ethylenediaminetetraacetate, and 0.9 mmol/L, and 125I-iodocyanopindolol 0.9 mmol/L, For saturation curves, eight concentrations of 125I-iodocyanopindolol were used (5 to 166 pmol/L) in each assay. For competition curves, one concentration of 125I-iodocyanopindolol (41 pmol/L) was used in each assay. The reaction was stopped after 90 minutes of incubation by addition of 10 ml 0.9% NaCl, 10 ml Tris HCl, and MgCh 12.5 mmol/L, followed by rapid filtration through Whatman GF/C filters (Whatman Inc., Clifton, N.J.) Each filter was then washed by an additional 5 ml of buffer. The radioactivity retained on the filter was determined with a -y-counter. Nonspe*Pharmacia Inc., Piscataway, N.J. tWinthrop Laboratories, New York, N.¥.

Table III. Mean plasma epinephrine and norepinephrine concentrations during the operation' (pgfml) Control Orotracheal intubation Sternal retraction BeforeCPB Aortic clamping CPB 30 min Defibrillation

135 ± 161 ± 120 ± 85 ± 128 ± 154 ± 221 ±

Norepinephrine

399 ± 362 ± 197 ± 223 ± 302 ± 339 ± 472 ±

19 59 55 15 37 24 40

44 54 33* 42* 54 48 65

Values are mean ± standard error of the mean. *p < 0.01 versus control.

Table IV. Variations in plasma epinephrine and norepinephrine levels during the operation in two subsets ofpatients Group I (n = 10) Control

Epinephrine 173 ± 21 (pgjml) . Norepineprhine 359 ± 46 (pg/rnl)

CPS

145 ± 23 327 ± 40

Group II (n = 6) Control

CPS

67 ± 12 216 ± 45*t 489 ± 94

471 ± 120

Values are mean ± standard error of the mean. Group I comprises patients without adrenergic activation during CPB and group II comprises patients with adrenergic activation during CPB.

*p < 0.0I versus control. tp < 0.0 I versus group I. cific binding was defined as that binding not competed for by (-) isoproterenol 0.1 mmol/L, Saturation experiments consisted of the fixation of incremental concentrations of I 25I-Iodocyanopindolol on the lymphocyte membrane preparation. ,a-Adrenergic receptor density (Bmax, femtomoles per milligram of protein), the dissociation constant for 125I-iodocyanopindolol (Kj, picomoles per liter), and nonspecific binding were determined by saturation experiments with a nonlinear computerized curve-fitting model according to the mass action law," Kct was defined as the concentration of 125I-iodocyanopindolol for which 50% ,a-adrenergic receptors were occupied and was an index of the affinity of the receptors for antagonist drugs. Competition was defined as the displacement of I 25I-iodocyanopindolol (41 pmol/L) from its receptor sites by incremental concentrations of nonlabeled isoproterenol. Isoproterenol was used at 13 concentrations (10- 9 to 10- 3 mol/L). The affinity of the J3-adrenergic receptors for J3-adrenergic agonists was assessed by calculation of the IC 50 (which is the isoproterenol concentration able to remove 50% of radiolabeled 125I_iodocy_ anopindolol from its receptors) using a nonlinear computerized curve fitting.? Lymphocyte protein concentration was determined by the method of Lowry and associates, 10 with bovine serum albumin used as standard. Plasmacatecholamine concentrations. Intraoperative adrenergic activity was assessed by repeated measurements of norepinephrine and epinephrine plasma levels during the operation.

78

The Journal of Thoracic and Cardiovascular

Mantz et al.

Surgery

Table V. Details of intraoperative hemodynamic data Control

MAP (mm Hg) HR (beats/min) Cl (L/min/m 2) SVR (dyne/sec/cm- S) PWP (mm Hg)

101 63 2.8 1596 11.1

± ± ± ± ±

3.5 3 0.2 97 0.75

Orotracheal intubation 91 63 2.5 1495 9.6

± ± ± ± ±

Sternal retractation 89 ± 62 ± 2.1 ± 1742 ± 8.2 ±

29 5 0.2 90 0.87

2.9 5 0.1 133 0.61

Aortic decannulation 66.5 ± 2.8* 85 ± 2* 2.4 ± 0.1 1195 ± 88* 12.1 ± 0.74

Values are mean ± standard error of the mean. MAP, Mean arterial pressure; HR, heart rate; CI, cardiac index; SVR, systemic vascular resistances; PWP, pulmonary wedge pressure. *p > 0.05 versus control.

Five-milliliter blood samples were withdrawn first just before anesthesia induction (control), then 1 minute after orotracheal intubation, 1 minute after sternal retraction, and every 30 minutes until the end of CPB. Additional samples were obtained whenever an abrupt increase in heart rate or blood pressure occurred during the operation. Plasma catecholamine concentrations were determined according to the method of Mefford and colleagues. I I Intraoperative adrenergic activation was considered present if plasma epinephrine or norepinephrine levelswere increased by at least 50% when compared with control values. Adrenergic activation was declared transient when it was found in only one measurement during the operation, It was considered sustained when present at least at three consecutive measurements. Statistical analysis. Data on ~-adrenoreceptor affinity and density, intraoperative catecholamine plasma levels,and hemodynamic variations concerning the 16 patients were compared by analysis of variance with the Bonferroni method when appropriate. Statistics involving small samples required the use of the nonparametric Wilcoxon test for paired data and the Mann-Whitney test for unpaired data; p < 0.05 was considered the threshold for significance. Clinical course. Postoperative outcome was uneventful in 12 patients. The three patients who required intraaortic balloon pumping because of severe cardiac failure after CPB cessation were able to leave the intensive care unit within 14 days. In two patients, limited myocardial necrosis was diagnosed in the first 24 postoperative hours on the basis of supportive electrocardiographic modifications and marked elevation of plasma MB creatine kinase levels.

Results No significant differences were found in receptordensity or affinity for agonists or antagonists between measurements taken just before anesthesia induction (control) and thosetaken at the end of CPB (Table 11). Mean plasma epinephrine and norepinephrine levels were not significantly altered during CPB (Table III). However, a sustained adrenergic activation was observed in six patients (group II) during CPB as assessed by a threefold increase in plasma epinephrine levels (Table IV). No adrenergic activation occurred during CPB in the other 10 patients (group I). In the six patients with adrenergic activation, the affinity of lymphocyte ~-adrenoreceptors for isoproterenol wassignificantly decreasedat the end of CPB (as assessed by an increase in IC 50 [+66%,

p < 0.05, Fig. I D. In contrast, IC 50valuesremainedun-

altered in the 10 patients who did not have high catecholamine levels during CPB. Moreover, an increase in IC 50wasfoundas wellin the three patientswhorequired intraaortic balloonpumping after CPB discontinuation. No significant modification either in densityor in affinity was observed in relation to adrenergic activation. Intraoperativehemodynamic data are summarizedin Table V. No significant change in mean heart rate, cardiac index,arterial pressure, pulmonarywedgepressure, and systemic vascular resistances was observed at intubation or sternal retraction. However, a sharp but transient increase in plasma catecholamine levels was observed at intubation together with an increase in heart rate and arterial pressure in two patients. At aortic decannulation, mean arterial pressureand systemic vascular resistances were significantly decreased and heart rate wasincreased (p < 0.05),whereascardiacindexwas unchanged when compared with control values. Discussion

Understandingthe factorspossiblyimplicated inadrenergic function changes is crucial to allowcorrect perioperative management of patients undergoing myocardial revascularization, becausecatecholamines are often necessary to support cardiac inotropism after CPB. The presentstudyshows that no modification in mean density and affinity of ~-adrenergic receptorsoccurredin patients undergoing coronary artery bypass grafting. However, stratification of the analysis shows that receptor affinity for ~-adrenergic agonists (isoproterenol) wasdecreased in the patients who had high plasma catecholamine levels duringCPB.In contrast,nosignificant modification inthe affinity for agonists was observed in the patientswhodid not have this degree of adrenergic activation. Other factors possibly involved in the alteration of ~­ adrenergic function (e.g., cardiac therapies, anesthetic regimens) do not seemto haveplayeda significant rolein the observed receptor changes. Chronic ~-adrenergic blockade has been shown to induce an increase.i a decrease, 12, 13 or no modification 14 in ~-adrenergic recep-

Volume 99 Number 1

{3-Adrenergic receptors and coronary artery operations

January 1990

BETA-RECEPTOR DENSITY 80 70

:: 40 30

~---------,

RECEPTOR AFFINITY FOR ANTAGONIST 50.,----------,

Bmax (fmollmg)

~::

40 30 GROUP 1 ,,0

20 10

10

o

O-l---.-~---r--~

CONTROL

80 60

BmQ~ . ....,-

40 20

30

.~

0

10

0

CONTROL

END OF CPB

END OF CPB

CONTROL

6000

Kd (pM)

5000

END OF CPB

IC50~

4000

20

GROUP 2

RECEPTOR AFFINITY FOR AGONIST

8000 ~-----------, IC50 (nM) 7000 8000 5000 GROUP 1 4000 GROUP 1 3000 2000 1000 o-l---.-~~-+-----l

CONTROL

END OF CPB

79

~...,-

~ CONTROL

GROUP 2 3000 2000 1000 0

END OF CPB

~CONTROL

GROUP 2

END OF CPB

Fig. 1. Individual variations of lymphocyte ,,-adrenergic receptor density and affinity for agonist and antagonist between anesthesia induction (control) and at end of cardiopulmonary bypass (end oICPB). Patients who required intraaortic balloon pumping at the end of CPB are identified by arrows, Bmax, iJ-Adrenergic receptor density; Kd, dissociation constant; IC 50, isoproterenol concentration able to remove 50% of radio labeled 125I-iodocyanopindolol from its receptors.

tor density. In contrast, neither nifedipine nor diltiazem has been demonstrated to significantly alter {3-adrenergic receptor density or affinity.P In the present study, cardiac therapies were similar in the two groups of patients. With respect to the influence of anesthetic agents on {3-adrenergic receptors, it has indeed been recently shown that the receptor density is decreased by halothane. 16 In this study, however, only narcotics were used, and they have not yet been reported to induce similar changes. Moreover, narcotic doses administered to the patients were similar in the two groups as well. It seems, therefore, that the most likely explanation for the observed {3-adrenergic receptor desensitization was the presence of high plasma catecholamine levels during CPB. Desensitization of lymphocyte {3-adrenergic receptors can be expected in all situations, including surgery, where marked adrenergic activation is present. Interestingly, {3-adrenergic receptor density was not modified in our patients, whatever the degree of intraoperative adrenergic activation. This suggests functional uncoupling of {3-adrenergicreceptors. Similar data have been reported by Feldman and associates- in healthy humans after acute elevation of plasma catecholamine levels. In contrast to previous studies, we did not find that all patients undergoing myocardial revascularization had high catecholamine plasma levels during the operation.

The striking differences observed between our study and that of Reves' group'? could be related in part to differences in anesthetic regimens. In fact, high doses of narcotics, which were used in our study, have been shown to blunt most hemodynamic responses resulting from adrenergic activation in most patients undergoing stressful surgical procedures." However, recent studies in which high doses of fentanyl were used for coronary artery bypass grafting have reported an elevation in plasma catecholamine concentrations during CPB in few patients only.19,20 The results reported by Massagee and associates-" are strikingly similar to ours: In fact, in their study, two subpopulations of patients can be separated on the basis of the presence or absence of adrenergic activation during CPB. Merlone and co-workers" have shown that potassium chloride infusion elicits an increase in plasma catecholamine levels during CPB. However, in our study, CPB conditions were the same for all patients. It is unclear why the affinity for isoproterenol was decreased at the end of CPB in the three patients who required intraaortic balloon pumping. In fact, plasma catecholamine levels remained unchanged for CPB in these patients except for one. It can be suggested that other factors might have affected {3-adrenergic responsiveness, primarily those that are known to worsen ventricular function after CPB (mechanical manipulation of the

80

Mantz et al.

heart, cooling, fibrillation, cardioplegia, and ischemia duration).22-26 However, no data are available on the effects of these factors on ,B-adrenergic function. Finally, because Brodde and associates I quite clearly assessed the validity of the lymphocyte model for reflecting changes occurring in myocardial ,B-adrenergic receptor function during cardiac operations it would be tempting to extrapolate our results to myocardial ,B-adrenergic responsiveness. We think, however, that further studies are necessary to directly assess the modifications of myocardial ,B-adrenergic function and contractility during coronary artery bypass grafting, taking into consideration that desensitization of myocardial ,B-adrenergic receptors primarily affects those of the,B1 subtype, which are not present on lymphocyte membranes.l? A better understanding of these phenomena would be helpful in improving the effectiveness of inotropic support in patients undergoing myocardial revascularization. We are grateful to Drs. Bohm, Depoix, Hazebroucq, and Videcocq for their help in the performance of this study and to Dr. P. Vezina for helping to improve the manuscript. REFERENCES I. Brodde OE, Kretsch R, Zerkowski HR, Ikezono HR, Reidemeister Jc. Human lymphocyte beta-adrenoreceptors: relation of myocardial and lymphocyte beta-adrenoreceptor density. Science 1986;231:1584-5. 2. Aarons RD, Molinoff PB. Changes in the density of betaadrenergic receptors in rat lymphocytes, heart and lungs after chronic treatment with propranolol. J Pharmacol Exp Ther 1982;221:439-43. 3. Lefkowitz RJ, Caron MC, Stiles GL. Mechanisms of membrane receptor regulation: biochemical, physiological and clinical insights derived from studies of the adrenergic receptors. N Engl J Med 1984;310:1570-9. 4. Fraser J, Nadeau J, Robertson D, Wood AJJ. Regulation of human leukocyte beta-receptors by endogenous catecholamines. J Clin Invest 1981;367:1777-84. 5. Feldman RD, Limbird LE, Nadeau J, Fitzgerald CA, Robertson D, Wood AJJ. Dynamic regulation of leukocyte beta-adrenergic receptor agonist interaction by physiological changes in circulating catecholamines. J Clin Invest 1983;72:164-70. 6. Marty J, Rocchiccioli C, Henzel D, Loiseau A, Desmonts JM. Is beta-adrenergic function altered in patients after surgery? Clin Res 1986;34:403A. 7. Mangano DT. Biventricular function after myocardial revascularization in humans: deterioration and recovery patterns during the first 24 hours. Anesthesiology 1985;62: 571-7. 8. Munson PJ, Rodbard D. A versatile computerized apptoach for characterization of ligand binding system. Anal Biochem 1980;107:220-39.

The Journal of Thoracic and Cardiovascular Surgery

9. Hancock AA, Delean AL, Lefkowitz RJ. Quantitative resolution of beta-adrenergic receptor subtype by selectivelingand binding: application of a computerized model fitting technique. Mol PharmacoI1979;16:1-9. 10. Lowry 0 H, Rosebrough N J, Farr AL, Randale RJ. Protein measurement with the Folin phenol reagent. J Bioi Chern 1951;193:265-75. II. Mefford IN, Ward NM, Miles L, et al. Determination of plasma catecholamines and free 3,4-dihydroxyphenylacetic acid in continuously collected human plasma by high performance liquid chromatography with electrochemical detection. Life Sci 1981;28:477-83. 12. De Blasi A, Fratelli M, Marasco O. Certain beta-blockers can decrease beta-adrenergic receptor number. 1.Acute reduction in the number of receptors by tertatol and bopindolol. Circ Res 1988;63:273-8. 13. Hughes RJ, Mahan LC, Insel PA. Certain beta-blockers can decrease beta-adrenergic receptor number. II. Down regulation of receptor number by alprenolol and propranolol in cultured lymphoma and muscle cells. Circ Res 1988;63:279-85. 14. CooperG, KentRL, McGornigleP, Watanabe AM. Betaadrenergic receptor blockade of feline myocardium: cardiac mechanisms, energetics and beta-adrenoceptor regulation. J Clin Invest 1986;77:441-54. 15. Feldman RD, Park GD, Lai CY. The interaction of verapamil and norverapamil with the beta-adrenergic receptors. Circulation 1985;72:547. 16. Marty J, Nivoche Y, Nimier M, et al. The effects of halothane on the human beta-adrenergic receptor of lymphocyte membranes. Anesthesiology 1987;67:974-8. 17. Reves JG, Karp RB, Tosone S, et al. Neuronal and adrenomedullary catecholamine release in response to cardiopulmonary bypass in man. Circulation 1982;66:49-54. 18. Stanley TH, Berman L, Green 0, Robertson D. Plasma catecholamine and cortisol responses to oxygen-fentanyl anesthesia for coronary artery operation. Anesthesiology 1980;53:250-3. 19. Tonnesen E, Brinklov MM, Christensen NJ, Olesen AS, Madsen T. Natural killer cell activity and lymphocyte function during and after coronary artery bypass grafting in relation to endocrine stress response. Anesthesiology 1987;67:526-33. 20. Massagee JT, McIntyre R W, Kates RA, Reves JG, Bai S. Effects of preoperative calcium entry blocker therapy on alpha adrenergic responsiveness in patients undergoing coronary revascularization. Anesthesiology 1987;67:48591. 21. Merlone S, Gaba D, Dauffenbach R, Fravert D, Smith C, Maze M. High time resolution catecholamine sampling during cardiopulmonary bypass. Anesthesiology 1985; 63:3A. 22. CASS Principal Investigators and their Associates. Myocardial infarction and mortality in the coronary artery surgery study (CASS) randomized trial. N Engl J Med 1984;310-750-8.

Volume 99 Number 1 January 1990

23. Berger RL, Davis KB, Kaiser GC, et al. Preservation of the myocardium during coronary artery bypass grafting. Circulation 1981;64(Pt 2):II61-6. 24. Kouchoukos NT, Oberman A, Kirklin JW, et al. Coronary bypass surgery: analysis of factors affecting hospital mortality. Circulation 1980;62(Pt 2):184-9. 25. Davis KB. Operative mortality in the CASS registry. Coronary bypass surgery. New York: Praeger, 1983:99.

{3-Adrenergic receptors and coronary arteryoperations 8 1

26. Cannom OS, Miller IDC, Shumway NE, et al. The long term follow-up of patients undergoing saphenous vein bypass surgery. Circulation 1974;49:77-85. 27. Bristow MR, Ginsburgh R, Urmans V, et al. (3 I and (32 adrenergic receptor subpopulations in nonfailing and failing human ventricular myocardium: coupling of both receptor subtypes to muscle contraction and selective (3 I down-regulation in heart failure. Circ Res 1986;59:297-309.

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