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ENDOTHELIN-1 IN DIABETIC AND NONDIABETIC MEN WITH ERECTILE DYSFUNCTION
oO22-6347/97/1585177W3.WO
Vol. 158, 1770-1774,November 1997 Printed in U.S.A
THE JOURNAL OF UROLOGY Copright 0 1997 by AMERICANUROLDGICAL ASS~CUTION,INC.
ENDOTHELIN-1 IN DIABETIC AND NONDIABETIC MEN WITH ERECTILE DYSFUNCTION SANDRO FRANCAWLLA, GIULIANA PROPERZI, CESARE BELLINI, GIOVA"1 W I N O , CLAUD10 FERRI AND ANNA SANTUCCI From the Departments
of
Internal Medicine and Surgery, University of L'Aquila, and Institute of I Cfinica Medica, University La Sapienza, Rome, Italy
ABSTRACT
Purpose: We evaluated plasma concentration of endothelin-1 in diabetic and nondiabetic men complaining of erectile dysfunction, and the variation of endothelin-1 in cavernous body blood during intracavernous injection of prostaglandin E 1. Materials and Methods: We evaluated plasma concentrations of endothelin- 1in venous blood of 20 men with erectile dysfunction, 10 with and 10 without diabetes. Plasma concentration of endothelin-1 was also evaluated in the cavernous body blood of the 20 men with erectile dysfunction, during erection induced by intracavernous injection of 10 p g . prostaglandin E l . A severe vasculogenic component of erectile dysfunction was excluded in all patients. Results: Basal plasma concentration of endothelin-1 in the cubital vein was increased in nondiabetic (1.13 -+ 0.4 pg./ml.) and in diabetic (1.80 ? 0.2 pg.lml.1 patients with erectile dysfunction, compared to control men (0.642 0.1 pg./ml.) (p <0.0005and p <0.0001, respectively), and in diabetic compared with nondiabetic patients (p <0.002).No difference and close correlation were observed in the concentration of endothelin-1 in the cavernous body blood evaluated 5 minutes and 30 minutes after injection of prostaglandin E l (r = 0.89, p <0.0001, y = 0.98 x + -0.066).The concentration of endothelin-1 in the cavernous body blood evaluated 30 minutes after injection of prostaglandin E l did not show any difference compared to peripheral venous concentration of the peptide in the 2 patient groups. Concentrations of endothelin-1 in the peripheral vein and the cavernous body blood were not different in patients with a full erection compared with incomplete penis erection after injection of prostaglandin E l in the cavernous body. Conclusions: Elevated plasma concentration of endothelin-1 in peripheral vein blood was indicative of endothelial dysfunction that might contribute to erectile failure. KEY WORDS:endothelins, penile erection, prostaglandins E, diabetes mellitus
Active corporeal smooth muscle relaxation is thought to be the pivotal step in generation of penile tumescence.' Impaired neural and endothelium-dependent smooth muscle relaxation has been demonstrated in cavernous tissue from impotent diabetic patients.* The defect, which could be a cause of erectile dysfunction with reported prevalence as high as 50% in diabetic men,3 is not restricted to the corpus cavernosum. Impaired endothelium-dependent vasodilatation has been demonstrated in patients with diabetes mellitus4 and may contribute to the pathogenesis of vascular disease that occurs frequently in such patients.5 Decreased synthesis or release of endothelium-derived relaxing factor has been proposed as a possible mechanism for endothelial dysfunction in corpus cavernosum of impotent diabetic patients.3 Endothelial cells lining sinusoids of cavernous tissue affect the tone of adjacent smooth muscle cells through release of endothelium derived relaxing factor, a nitric oxide related molecule,6 and also through the release of vasoactive agents such as endothelin-1.7 Endothelin-1 is a potent arterial and venous vasoconstrictor peptide that functions as circulating hormone and paracrine factor in the regulation of vascular tone.8 Elevated plasma levels of endothelin-1 were found in peripheral venous blood from patients with diabetes m e l l i t ~ sWe . ~ analyzed plasma concentration of endothelin-1 in men with or without diabetes, complaining of erectile
dysfunction that was not associated with a severe vasculogenic defect. Endothelin-1 plasma levels were evaluated in peripheral venous blood and in cavernous body blood during erection induced by intracavernous injection of prostaglandin E1.10 MATERIALS AND METHODS
Patients and protocol. Informed consent to participate in the study was obtained from each subject. Twenty men with erectile dysfunction (consistent inability to achieve or sustain a sufficiently rigid erection for sexual intercourse) for more than 1 year were enrolled. Of 10 patients (mean age 48 years 2 6.5) with a history of C-peptide positive diabetes mellitus for more than 4 years, 6 were taking insulin and 4 were taking oral hypoglycemic agents. Patients on insulin treatment were not younger than the other patients. The remaining 10 patients not affected by diabetes were younger (p <0.005) compared to the diabetic patients (mean age 35 years 5 8.4) (table 1). None had a history of alcoholism or of smoking more than 8 cigarettes per day. Initial evaluation included sexual history, physical examination and electrocardiogram. Blood evaluation of total testosterone, thyroidstimulating hormone, free thyroxin and prolactin excluded endocrinological diseases. All patients were tested for bulbocavernous reflex, measured electrically, to test the integrity of the sacral arc. Bulbocavernous reflex was abnormal in 4 Accepted for publication March 14, 1997. Supported by Ministem dell' Universith e della Ricerca Scientifica, diabetic men (table 1). All patients had a normal penile Rome, Italy. brachial index (greater than 0.7). Ultrasonographic evalua1770
1771
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION TABLE1. Characteristics, laboratory parameters and plasma level of endothelin-1 of patient population Mean P g M . (SD)
-
Diabetic (10 pta.,
Nondiabetic (10 pts.)
48 (6.5) 35 (8.4) Age (P.) 30% 20% Smokers Bulbocavernous reflex abnormal 0% 40% Erection after prostaglandin E l 64% 40% Endothelin-1 cubital vein basal 1.13 (0.4) 1.80 (0.2) Endothelin-1 cubital vein 30 min. 2.00 (0.2) 1.38 (0.6) after prostaglandin E l Endotbelin-1 intracavernous 5 2.07 (0.3) 1.17 (0.6) mins. after prostaglandin E l Endothelin-1 intracavernous 30 2.14 (0.2) 1.29 (0.5) min. after prostaglandin E l Statistical analysis by Student t test for independent samples.
0.001
0.001 0.011 0.001 O.OOO1
tion of cavernous arteries, performed within 5 minutes after injection of 10 pg. prostaglandin E l in the right corpus cavemosum with the patient supine, showed a systolic flow rate of greater than 21 cm. per second. Therefore, patients were categorized as not having a severe arteriogenic component of erectile dysfunction.ll Ten normal male volunteers (mean age 38 years +- 7.9, p <0.01 compared to diabetic patients, and p nonsignificant compared to nondiabetic patients) were enrolled as the control group. Evaluation of plasma endothelin-1. Patients were readmitted to the outpatient clinic 2 weeks after the first evaluation and 10 ml. of blood were obtained from an antecubital vein after at least 15 minutes of supine rest. Plasma concentration of endothelin-1 in the venous blood of the 20 patients was collected before prostaglandin E l iqjection and compared to that of the control group. In a preliminary study we tried to obtain blood samples from the cavernous body of patients with erectile dysbction in a flaccid state. Results were disappointing, so that blood samples were obtained from the cavernous body during erection induced by intracavernous injection of prostaglandin E1.10 Ten c~g.prostaglandin E l diluted in 1 ml. normal saline were injected in the right cavernous body with a 27 gauge needle. Five minutes after prostaglandin E l injection, 10 ml. of blood were collected from the left cavernous body with a 21 gauge needle. After sampling the cavernous needle was flushed with potassium ethylenediaminetetraacetic acid and sealed. Blood samples were collected from the ankubital vein and cavernous body 30 minutes after prostaglandin E l injection. Erectile response was evaluated by inspection and palpation by the same physician ( S . F.) and classified as suEcient or insufficient for sexual intercourse. All blood samples were collected into chilled K ' ethylenediaminetetraacetic acid (1mglml.) tubes treated with Aprotinin (500 kallikmin-inhibiting Units per ml. blood) and placed on ice immediately. Blood was separated by centrifugation at 4C (3,000 X g. for 10 minutes), and plasma was stored at -2OC until assay. One ml. of plasma was passed through CISoctyloecyildane colu m n ~ *previously activated with 0.1% trinuoracetic acid. To Separate endothelin-1 from other endothelin isoforms and large endothelin-1, each eluate was then ikezedn'ed,reconstituted starting high press~leliquid chromatography buffer, and eluted by kverse'phase hi&- pressure liq
in triplicate on the reconstituted Gaction by sensitive radioimmun0assay.t Human endothelin-l$ was used as standard. Interassay and intra-assay variatiom were less than lM. Cross-reactivity of endothelin-1autibodywith endohlin-2 and endothelin-3 was less than 796,according to the supplier. Statistical a d y s i s . Results of quantitative studies were. expressed as mean plus or minus standard deviation. Statistical comparison of plasma concentration of endothelin-1 in cubital vein blood of the 3 groups of men (control, diabetic and nondiabetic) was performed using ANOVA followed by the Fisher least significant difference test of repeated measures. Differencesbetween measures obtained in the 2 groups of patients were evaluated with the Student t test for independent samples. Single Student t teat for dependent samples was used to compare concentrations of endothelin-1 before and after prostaglandin E l isiection and to compare endothelin-1 concentration in patients with full and incomplete erection. Statistical analysis was performed with computer statistical s o h a r e . RESULTS
Concentrations of endothelin-1 in cubital vein blood of healthy men and men with erectile dysfunction. Plasma endothelin-1 concentration in cubital vein blood of healthy men was 0.64 2 0.1 pglml. and was significantly lower when compared to nondiabetic (1.13 2 0.4 pglml.) and diabetic (1.80 5 0.2 pglml.) patients (the Fisher least significant difference test p <0.0005 and p <0.0001,respectively) (fig. 1). Concentrations of endothelin-1 in eubital vein and cnuemous body blood of men with erectile dysfinction a f i r intmcavernus injection of prostaglandin E l . Basal plasma endothelin-1 concentration in cubital vein blood was significantly more elevated in diabetic (1.80 2 0.2 pglml.) compared to nondiabetic (1.13 2 0.4 pgJml.) patients (p eO.002, Student t test for independent samples) (table 1). Thirty minutes aRer intracavernous dection of 10 pg. of prostaglandin El, a slight increase in cubital vein blood concentration of endothelin-1 was observed in the 2 groups. Concentration of endothelin-1 was 2.00 -C 0.2 pglml. in diabetic and 1.38 t 0.6 pglml. in nondiabetic patients (p >0.05 and p <0.05, respectively, in the 2 groups,the difference between endothelin-1 concentration before and 30 minutes after injection of prostaglandin E l , after performing a single t test for dependent samples). Due to the small size of the study groups, the variation in endothelin-1 concentration before and after injection of prostaglandin E l was not considered significant. Endothelin-1 in cauerrwus body blood. The intracavernous level of endothelin-1 was more elevated in diabetic compared to nondiabetic patients 5 minutes (p <0.002, Student's t test for independent samples) and 30 minutes (p <0.001) after injection of prostaglandin El (table 1).The invasive procedure of blood collection from the cavernous body during erection did not allow a control group of normal men. However, the test performed in 3 men, 37,39 and 43 years old, with premature ejaculation and normal erection during sexual intercourse, showed no difference in the peripheral vein blood concentration of endothelin-1 from normal men. In these 3 Datients. the Dlasma concentration of endothelin-1 in cubital Lein and cavernous body blood was lower than the 95% confidence intervals of patients with erectile dysfunction. The 20 patients with erectile dysfunction did not show significant variation in endothelin-1 concentration in cavernous body plasma collected 5 minutes and 30 minutes after prostaglandin E l injection (single t test for dependent samples). A close correlation was noted between intracavemous concentration of endotheh-1 at 5 minutes and 30 minutes
t Penipsula L+mratories, Belmont, $ Pepbde Insbtute, Osaka. Japan.
California.
1772
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION
+
TABLE2. Plasma level of endothelin-1 in diabetic and nondiabetic men with full or incomplete erection after intmcavernous injection of 10 pg. prostaglandin E l Mean Pg./MI. tSD)
-
n
W
4
I
+ w
0.8
0.6 0.4 0.2 C
A
B
FIG. 1. Plasma endothelin-1 concentration in cubital vein of 10 healthy subjects ( C ) ,10 nondiabetic (A) and 10 diabetic ( B )patients with erectile dysfunction. Values are mean plus or minus standard deviation. * <0.0005 versus C. + p <0.00001 versus A and versus C ANOVA r)ollowed by Fisher least significant difference test of repeated samples.
Diabetic pts.: No. pts. Endothelin-1 cubital vein basal Endothelin-1 cubital vein 30 min. after prostaglandin El Endothelin-1 intracavernous 5 min. after prostaglandin El Endothelin-1 intracavernous 30 min. after prostaglandin E l Nondiabetic pts.: No. pts. Endothelin-1 cubital basal Endothelin-1 cubital vein 30 min. after prostaglandin E l Endothelin-1 intracavernous 5 min. &r prostaglandin E l Endothelin-1 intracavernous 30 min. after prostaglandin E l Statistical analysis with Student's t
P Level
Full Erection
Incomplete Erection
4 1.7 (0.2) 2.1 (0.2)
6 1.8 (0.2) 1.9 (0.2)
0.47 0.16
2.2 (0.1)
2.0(0.1)
0.23
2.3 (0.2)
2.0 (0.3)
0.06
6
0.9 (0.4) 1.1 ( 0 . 5 )
4 1.4 10.5) 1.8 10.7)
0.11 0.13
1.0 (0.6)
1.5 (0.7)
0.24
1.1 (0.4)
1.6 (0.6)
0.21
test for independent samples.
patients with incomplete erection aRer prostaglandin E l injection had intracavernous levels of endothelin-1 in the high range, suggesting that patients with high intracavernous levels of endothelin-1 have more chance to show incomplete erection after intracavernous injection of prostaglandin E 1.
after prostaglandin E l injection (fig. 2) (r = 0.89, p <0.0001, y = 0.980 x + -0.066).Endothelin-1 concentration evaluated 30 minutes after prostaglandin E l injection did not show a significant difference between cavernous body and cubital DISCUSSION vein blood in the study groups (table 1). Our investigation showed that diabetic and nondiabetic Endothelin-1 in cubital vein and cavernous body blood of men with erectile dysfunction had significantly increased patients with full or incomplete erection after prostaglandin peripheral venous endothelin-1 level than normal men. InEl injection. Plasma concentration of endothelin-1 in cubital duction of corporeal smooth muscle relaxation by intracavvein and cavernous body blood was not significantly different ernous prostaglandin E l injection in men with erectile dysin diabetic and nondiabetic patients with full erection Comfunction was not associated with significant variation of pared to patients with incomplete erection achieved after endothelin-1 in cavernous body blood or peripheral vein injection of 10 pg. prostaglandin E l (table 2), suggesting that blood, and no difference was observed between levels of concentration of endothelin-1 in the cavernous body blood endothelin-1 in peripheral vein and cavernous blood in all and peripheral vein system was not predictive of penile erec- patients. Endothelin-1 was not measured in cavernous body tion efficacy induced by intracavernous injection of 10 pg. blood of normal men due t o the invasive nature of the prostaglandin E l . However, figure 2 shows that 8 of 10 procedure. Therefore, it is questionable whether levels of endothelin-1 reported in cavernous body blood of patients with erectile dysfunction were more elevated than in normal A men. However, 2 observations support this hypothesis. Cav'I 3 t ernous body blood endothelin-1 level in 3 patients affected by premature ejaculation and normal penis erection was lower than that observed in men with erectile dysfunction. Correlation was present between peripheral vein and cavernous body blood concentrations of endothelin-1 in all patients, 0 suggesting that elevated peptide level in peripheral vein h blood in men with erectile dysfunction was associated with 1 . 5 + elevated endothelin-1 concentration in cavernous body blood. Impaired endothelium dependent smooth muscle relaxation n 1 I has been demonstrated in cavernous tissue from diabetic men with impotence.2 The finding of elevated endothelin-1concentration in periphA eral venous blood and in cavernous body blood of diabetic men I I with erectile dysfunction suggests that impaired endothelium I dependent smooth muscle relaxation in corpus cavernosum* I0.5 1 1.5 2 2. s and in forearm resistance vessels of diabetic men4 could be due w E T - 1 IC 3 0 ' pomt P G E l (pg/ml) to the same endothelial dysfunction (reduced release) of endoRG.2. Relation of plasma endothelin-1 concentration in cavern- thelium derived relaxing factor as proposed by others2.4 and to ous body blood of 20 patients with erectile dysfunction, 5 minutes increased endothelin-1 release. Elevated plasma levels of after injection of 10 pg. prostaglandin E l in corpus cavernosum, to endothelin-1were reported in patients with atherosclerosis and plasma endothelin-1intracavemous concentration 30 minutes after might be related to diffuse endothelial cell dysfunction.12 Inprostaglandin E l iqjection. Dashed lines indicate predicted 95% confidence intervals,r = 0.89, p <0.0001, y = 0.980 x + -0.066. A, creased immunoreactivity for endothelin-1 in atherosclerotic patienta with full erection.0,patients with incomplete erection after carotid arteries compared to normal vessels and increased prostaglandin E l injection. plasma levels of endothelin-1were described in men with clin-
1773
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION
ical atherosclerosis.'2 Plasma and tissue endothelin-1 immunoreactivity was enhanced in early atherosclerosis induced by Our study revealed elevated circulating endothelin-1levels hsercholesterolemia in pigs, and coexisted with abnormal in diabetic and nondiabetic men with erectile dysfunction endothelium-dependent vasodilatation.13 Lncreased immunore- compared with normal men, and plasma endothelin-1 levels activity for endothelin-1 was shown in cutaneous vessels in men in cavernous body blood comparable to levels in peripheral with diabetes for less than 10 years compared with controls.14 vein blood. This result is indicative of endothelial dysfunction All of these findings suggest that elevated circulating that might contribute to erectile failure. Absence of a severe endothelin-1 levels may reflect local overproduction of peptide vasculogenic component of erectile failure suggests that infrom damaged endothelid cells with plasma spillover. creased plasma levels of endothelin-1 could be related to The target of endothelin-1 is neighboring muscle cell where early atherosclerotic disease. Results also suggest that evalendothelin-1 is maximally retained under pathological con- uation of endothelin-1 levels in peripheral vein blood is a ditions associated with increased plasma endothelin-1 lev- clinical marker of diffise endothelial disease manifested by els.':' Since endothelin-1 has properties as vasoconstrictofl erectile dysfunction. Concentration of endothelin-1 in cavernand growth factorlS acting through specific endothelin-A re- ous body blood and peripheral vein system was not predictive ceptors,16 we suggest that increased local endothelin-1 re- of penile erection efficacy induced by intracavernous injeclease during early atherosclerosis might contribute to patho- tion of 10 pg. prostaglandin E l . genesis of vascular changes and altered vascular tone present in clinical atherosclerosis.'3 Endothelin-1, produced by the endothelium in human corpus cavernosum, contracts corporeal smooth muscle acting through a receptor mediated REFERENCES effect.7 Elevated circulating levels of endothelin-1 suggest that erectile dysfunction in diabetic and nondiabetic men 1. Saenz de Tejada, I., Goldstein, I. and Krane, R. J.: Local control might be evidence of diffuse endothelial dysfunction. Excluof penile erection. Urol. Clin. N. Amer.. 15: 9, 1988. 2. Saenz de Tejada, I., Goldstein, I., Azadzoi, K. M., Krane, R. J. sion from the study of patients with severe vasculogenic and Cohen, R. A,: Impaired neurogenic and endotheliumerectile failure component suggests that endothelial dysfuncmediated relaxation of penile smooth muscle from diabetic tion might be related to initial atherosclerotic disease. men with impotence. New Engl. J. Med., 320: 1025, 1989. It is unlikely that a spillover of endothelin-1 exclusively 3. McCulloch, D. K., Campbell, I. W., Wu, F. C., Prescott, R. J. and from altered endothelial cells of corpus cavernosum might Clarke, B. F.: The prevalence of diabetic impotence. Diabetomaintain elevated circulating peptide levels, considering logia, 18: 279, 1980. rapid degradation of circulating peptide from lungs, kidney 4. Jhonstone, M. T., Creager, S. J., Scales, K M., Cusco, J. A., Lee, and liver,17 and catabolism of endothelin-1 by vascular B. K. and Creager, M. A.: Impaired endotheliumdependent smooth muscle cells.lS Altered relaxation of penile smooth vasodilation in patients with insulindependent diabetes mellitus. Circulation, 88:2510, 1993. muscle cells from diabetic men with erectile dysfunction has 5. Garcia, M. J., McNamara, P. M., Gordon, T. and h e l l , W. B.: been demonstrated.* Animal19 and human2 studies suggest Morbidity and mortality in diabetics in the Framingham popthat this result is due principally to impaired release of ulation. Sixteen year follow-up study. Diabetes, 23: 105. 1974. nitrous oxide from nonadrenergic noncholinergic nerve fibers 6. Saenz de Tejada, I., Blanco, R., Goldstein, I., Azadzoi, A., de las of corpus cavernosum.2 This is thought to be related to reMorenas, R., Krane, J. and Cohen, A.: Cholinergic neurotransduction of penile nitric oxide synthase,lSan enzyme activity mission in human corpus cavernosum. Responses to isolated normally present in human cavernous nerves and their tertissue. h e r . J. Physiol., 264: H459, 1988. minal endings within corporal erectile tissue and nerve plex7. Saenz de Tejada, I., Carson, M. P., De Las Morenas, A.. uses in the adventitia of deep cavernous arteries.2O Although Goldstein, I. and Traish, A. M.: Endothelin: localization, synthesis, activity, and receptor types in human penile corpus nitric oxide synthase has not been localized in endothelium cavernosum. h e r . J. Physiol., 261: H1078, 1991. lining vascular lacunae of the cavernous body,20 it has been 8. Rubanyi, G. M. and Boteho, L. H.: Endothelins. FASEB J., 5: shown that nitrous oxide or another closely related molecule 2713, 1991. acts as endothelium-derived relaxing substance in penile 9. Takahashi, K., Ghatei, M. A., Lam,H.-C., OHalloran, D. J. and smooth muscle.6 Bloom, S. R.: Elevated plasma endothelin in patients with Based on these findings and on results of our study, we diabetes mellitus. Diabetologia, 33:306, 1990. suggest that diabetes mellitus impairs endothelium depen- 10. Godschalk, M. F., Chen, J., Katz, P. G. and Mulligan, T.: Treatdent and neurogenic relaxation of penile smooth muscle of ment of erectile failure with prostaglandin El: a double-blind, diabetic men, due to impaired release of nitrous oxide from placebo-controlled, dose-response study. J. Urol., 161: 1530, nonadrenergic noncholinergic nerves and imbalance of a re1994. laxing nitrous oxide related molecule and a contracting 11. Hwang, T. I.-S.,Liu, P.-2. and Yang, C.-R.: Evaluation of penile dorsal arteries and deep arteries in arteriogenic impotence. endothelin-1 from endothelial cells. A study performed on J. Urol., 146.46, 1991. cavernous tissue from diabetic and nondiabetic men with erectile dysfunction showed in the former group an altered 12. Lerman, A., Edwards, B. S., Hallett, J. W., Heublein, D. M., Sandberg, S. M. and Burnett, J. C., Jr.: Circulating and tissue neuroendothelium and endothelium dependent relaxation endothelin immunoreactivity in advanced atherosclerosis. compared to the latter group.2 However, the integrity of the New Engl. J. Med., 326: 997, 1991. smooth muscle cell relaxing mechanism in normal men is not 13. Lerman, A., Webster, M. W., Chesebro, J. H., Edwards, W. D., known because cavernous tissue from normal men has not Wei, C.-M., Fuster, V. and Burnett, J. C., Jr.: Circulating and been evaluated. tissue endothelin immunoreactivity in hypercholesterolemic pigs. Circulation, 88: 2923, 1993. Although an altered neuro-dependent relaxation of corpus cavernosum cannot be ruled out in nondiabetic patients, the 14. Roperzi, G., Terenghi, G., Gu, X.-H., Poccia. G., Pasqua, R., Francavilla, S. and Polak, J. M.: Early increase precedes a finding of increased endothelin-1 concentration in the cubital depletion of endothelin-1 but not of Von Willebrand factor in vein of nondiabetic men with erectile dysfunction compared cutaneous microvessels of diabetic patients. A quantitative to normal men, and the finding of endothelin-1 concentration immunohistochemical study. J. Path., 175: 243, 1995. in cavernous blood of the same magnitude compared to cubi- 15. Bobik, A,, Grooms, A,, Millar, J. A,, Mitchell, A. and Grinpukel, tal vein is indicative of endothelial dysfunction in nondiaS.: Growth factor activity of endothelin on vascular smooth betic men with erectile failure. Increased endothelin-1 remuscle. Amer. J. Physiol., 268: C408, 1990. ' lease from altered endothelial cells in cavernous tissue might 16. Arai, H., Hori, S., Aramori, I., Ohkubo, H. and Nakanishi, S.: contribute to erectile dysfunction through its direct contractCloning and expression of a cDNA encoding an endothelin receptor. Nature, 348:730, 1990. h g effect on smooth muscle cells.? CONCLUSIONS
1774
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION
17. Pernow, J., Hemsen, A., Lundberg, J. M.: Tissue specific distri-
bution, clearance and vascular effects of endothelin in the pig. Biochem. Biophys. Res. Comm., 161: 647, 1989. 18. Jackman, H. L., Moms, P. W., Deddish, P. A,, Skidgel, R. A. and Erdos, E. G.: Inactivation of endothelin 1 by deamidase (lysosoma1 protective protein). J. Biol. Chem., 261: 2872, 1992. 19. Vernet, D., Cai, L., Garban, H., Babbitt, M. L., Murray, F. T., Rajfer, J. and Gonzalez-Cadavid, N. F.: Reduction of penile
nitric oxide synthase in diabetic BFVWORdp (Type I ) and BBZ/ WORdp (Type 11) rats with erectile dyshnction. Endocrinology, 136 5709, 1995. 20. Burnett, A. L., Tillman, S. L., Chang, T. S. K, Epstein, J. I., Lowenstein, C. J., Bredt, D. S., Snyder, S. H. and Walsh, P. C.: Immunohistochemical localization of nitric oxide synthase in the autonomic innervation of the human penis. J. Urol., 150: 73. 1993.
Vol. 158, 1770-1774,November 1997 Printed in U.S.A
THE JOURNAL OF UROLOGY Copright 0 1997 by AMERICANUROLDGICAL ASS~CUTION,INC.
ENDOTHELIN-1 IN DIABETIC AND NONDIABETIC MEN WITH ERECTILE DYSFUNCTION SANDRO FRANCAWLLA, GIULIANA PROPERZI, CESARE BELLINI, GIOVA"1 W I N O , CLAUD10 FERRI AND ANNA SANTUCCI From the Departments
of
Internal Medicine and Surgery, University of L'Aquila, and Institute of I Cfinica Medica, University La Sapienza, Rome, Italy
ABSTRACT
Purpose: We evaluated plasma concentration of endothelin-1 in diabetic and nondiabetic men complaining of erectile dysfunction, and the variation of endothelin-1 in cavernous body blood during intracavernous injection of prostaglandin E 1. Materials and Methods: We evaluated plasma concentrations of endothelin- 1in venous blood of 20 men with erectile dysfunction, 10 with and 10 without diabetes. Plasma concentration of endothelin-1 was also evaluated in the cavernous body blood of the 20 men with erectile dysfunction, during erection induced by intracavernous injection of 10 p g . prostaglandin E l . A severe vasculogenic component of erectile dysfunction was excluded in all patients. Results: Basal plasma concentration of endothelin-1 in the cubital vein was increased in nondiabetic (1.13 -+ 0.4 pg./ml.) and in diabetic (1.80 ? 0.2 pg.lml.1 patients with erectile dysfunction, compared to control men (0.642 0.1 pg./ml.) (p <0.0005and p <0.0001, respectively), and in diabetic compared with nondiabetic patients (p <0.002).No difference and close correlation were observed in the concentration of endothelin-1 in the cavernous body blood evaluated 5 minutes and 30 minutes after injection of prostaglandin E l (r = 0.89, p <0.0001, y = 0.98 x + -0.066).The concentration of endothelin-1 in the cavernous body blood evaluated 30 minutes after injection of prostaglandin E l did not show any difference compared to peripheral venous concentration of the peptide in the 2 patient groups. Concentrations of endothelin-1 in the peripheral vein and the cavernous body blood were not different in patients with a full erection compared with incomplete penis erection after injection of prostaglandin E l in the cavernous body. Conclusions: Elevated plasma concentration of endothelin-1 in peripheral vein blood was indicative of endothelial dysfunction that might contribute to erectile failure. KEY WORDS:endothelins, penile erection, prostaglandins E, diabetes mellitus
Active corporeal smooth muscle relaxation is thought to be the pivotal step in generation of penile tumescence.' Impaired neural and endothelium-dependent smooth muscle relaxation has been demonstrated in cavernous tissue from impotent diabetic patients.* The defect, which could be a cause of erectile dysfunction with reported prevalence as high as 50% in diabetic men,3 is not restricted to the corpus cavernosum. Impaired endothelium-dependent vasodilatation has been demonstrated in patients with diabetes mellitus4 and may contribute to the pathogenesis of vascular disease that occurs frequently in such patients.5 Decreased synthesis or release of endothelium-derived relaxing factor has been proposed as a possible mechanism for endothelial dysfunction in corpus cavernosum of impotent diabetic patients.3 Endothelial cells lining sinusoids of cavernous tissue affect the tone of adjacent smooth muscle cells through release of endothelium derived relaxing factor, a nitric oxide related molecule,6 and also through the release of vasoactive agents such as endothelin-1.7 Endothelin-1 is a potent arterial and venous vasoconstrictor peptide that functions as circulating hormone and paracrine factor in the regulation of vascular tone.8 Elevated plasma levels of endothelin-1 were found in peripheral venous blood from patients with diabetes m e l l i t ~ sWe . ~ analyzed plasma concentration of endothelin-1 in men with or without diabetes, complaining of erectile
dysfunction that was not associated with a severe vasculogenic defect. Endothelin-1 plasma levels were evaluated in peripheral venous blood and in cavernous body blood during erection induced by intracavernous injection of prostaglandin E1.10 MATERIALS AND METHODS
Patients and protocol. Informed consent to participate in the study was obtained from each subject. Twenty men with erectile dysfunction (consistent inability to achieve or sustain a sufficiently rigid erection for sexual intercourse) for more than 1 year were enrolled. Of 10 patients (mean age 48 years 2 6.5) with a history of C-peptide positive diabetes mellitus for more than 4 years, 6 were taking insulin and 4 were taking oral hypoglycemic agents. Patients on insulin treatment were not younger than the other patients. The remaining 10 patients not affected by diabetes were younger (p <0.005) compared to the diabetic patients (mean age 35 years 5 8.4) (table 1). None had a history of alcoholism or of smoking more than 8 cigarettes per day. Initial evaluation included sexual history, physical examination and electrocardiogram. Blood evaluation of total testosterone, thyroidstimulating hormone, free thyroxin and prolactin excluded endocrinological diseases. All patients were tested for bulbocavernous reflex, measured electrically, to test the integrity of the sacral arc. Bulbocavernous reflex was abnormal in 4 Accepted for publication March 14, 1997. Supported by Ministem dell' Universith e della Ricerca Scientifica, diabetic men (table 1). All patients had a normal penile Rome, Italy. brachial index (greater than 0.7). Ultrasonographic evalua1770
1771
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION TABLE1. Characteristics, laboratory parameters and plasma level of endothelin-1 of patient population Mean P g M . (SD)
-
Diabetic (10 pta.,
Nondiabetic (10 pts.)
48 (6.5) 35 (8.4) Age (P.) 30% 20% Smokers Bulbocavernous reflex abnormal 0% 40% Erection after prostaglandin E l 64% 40% Endothelin-1 cubital vein basal 1.13 (0.4) 1.80 (0.2) Endothelin-1 cubital vein 30 min. 2.00 (0.2) 1.38 (0.6) after prostaglandin E l Endotbelin-1 intracavernous 5 2.07 (0.3) 1.17 (0.6) mins. after prostaglandin E l Endothelin-1 intracavernous 30 2.14 (0.2) 1.29 (0.5) min. after prostaglandin E l Statistical analysis by Student t test for independent samples.
0.001
0.001 0.011 0.001 O.OOO1
tion of cavernous arteries, performed within 5 minutes after injection of 10 pg. prostaglandin E l in the right corpus cavemosum with the patient supine, showed a systolic flow rate of greater than 21 cm. per second. Therefore, patients were categorized as not having a severe arteriogenic component of erectile dysfunction.ll Ten normal male volunteers (mean age 38 years +- 7.9, p <0.01 compared to diabetic patients, and p nonsignificant compared to nondiabetic patients) were enrolled as the control group. Evaluation of plasma endothelin-1. Patients were readmitted to the outpatient clinic 2 weeks after the first evaluation and 10 ml. of blood were obtained from an antecubital vein after at least 15 minutes of supine rest. Plasma concentration of endothelin-1 in the venous blood of the 20 patients was collected before prostaglandin E l iqjection and compared to that of the control group. In a preliminary study we tried to obtain blood samples from the cavernous body of patients with erectile dysbction in a flaccid state. Results were disappointing, so that blood samples were obtained from the cavernous body during erection induced by intracavernous injection of prostaglandin E1.10 Ten c~g.prostaglandin E l diluted in 1 ml. normal saline were injected in the right cavernous body with a 27 gauge needle. Five minutes after prostaglandin E l injection, 10 ml. of blood were collected from the left cavernous body with a 21 gauge needle. After sampling the cavernous needle was flushed with potassium ethylenediaminetetraacetic acid and sealed. Blood samples were collected from the ankubital vein and cavernous body 30 minutes after prostaglandin E l injection. Erectile response was evaluated by inspection and palpation by the same physician ( S . F.) and classified as suEcient or insufficient for sexual intercourse. All blood samples were collected into chilled K ' ethylenediaminetetraacetic acid (1mglml.) tubes treated with Aprotinin (500 kallikmin-inhibiting Units per ml. blood) and placed on ice immediately. Blood was separated by centrifugation at 4C (3,000 X g. for 10 minutes), and plasma was stored at -2OC until assay. One ml. of plasma was passed through CISoctyloecyildane colu m n ~ *previously activated with 0.1% trinuoracetic acid. To Separate endothelin-1 from other endothelin isoforms and large endothelin-1, each eluate was then ikezedn'ed,reconstituted starting high press~leliquid chromatography buffer, and eluted by kverse'phase hi&- pressure liq
in triplicate on the reconstituted Gaction by sensitive radioimmun0assay.t Human endothelin-l$ was used as standard. Interassay and intra-assay variatiom were less than lM. Cross-reactivity of endothelin-1autibodywith endohlin-2 and endothelin-3 was less than 796,according to the supplier. Statistical a d y s i s . Results of quantitative studies were. expressed as mean plus or minus standard deviation. Statistical comparison of plasma concentration of endothelin-1 in cubital vein blood of the 3 groups of men (control, diabetic and nondiabetic) was performed using ANOVA followed by the Fisher least significant difference test of repeated measures. Differencesbetween measures obtained in the 2 groups of patients were evaluated with the Student t test for independent samples. Single Student t teat for dependent samples was used to compare concentrations of endothelin-1 before and after prostaglandin E l isiection and to compare endothelin-1 concentration in patients with full and incomplete erection. Statistical analysis was performed with computer statistical s o h a r e . RESULTS
Concentrations of endothelin-1 in cubital vein blood of healthy men and men with erectile dysfunction. Plasma endothelin-1 concentration in cubital vein blood of healthy men was 0.64 2 0.1 pglml. and was significantly lower when compared to nondiabetic (1.13 2 0.4 pglml.) and diabetic (1.80 5 0.2 pglml.) patients (the Fisher least significant difference test p <0.0005 and p <0.0001,respectively) (fig. 1). Concentrations of endothelin-1 in eubital vein and cnuemous body blood of men with erectile dysfinction a f i r intmcavernus injection of prostaglandin E l . Basal plasma endothelin-1 concentration in cubital vein blood was significantly more elevated in diabetic (1.80 2 0.2 pglml.) compared to nondiabetic (1.13 2 0.4 pgJml.) patients (p eO.002, Student t test for independent samples) (table 1). Thirty minutes aRer intracavernous dection of 10 pg. of prostaglandin El, a slight increase in cubital vein blood concentration of endothelin-1 was observed in the 2 groups. Concentration of endothelin-1 was 2.00 -C 0.2 pglml. in diabetic and 1.38 t 0.6 pglml. in nondiabetic patients (p >0.05 and p <0.05, respectively, in the 2 groups,the difference between endothelin-1 concentration before and 30 minutes after injection of prostaglandin E l , after performing a single t test for dependent samples). Due to the small size of the study groups, the variation in endothelin-1 concentration before and after injection of prostaglandin E l was not considered significant. Endothelin-1 in cauerrwus body blood. The intracavernous level of endothelin-1 was more elevated in diabetic compared to nondiabetic patients 5 minutes (p <0.002, Student's t test for independent samples) and 30 minutes (p <0.001) after injection of prostaglandin El (table 1).The invasive procedure of blood collection from the cavernous body during erection did not allow a control group of normal men. However, the test performed in 3 men, 37,39 and 43 years old, with premature ejaculation and normal erection during sexual intercourse, showed no difference in the peripheral vein blood concentration of endothelin-1 from normal men. In these 3 Datients. the Dlasma concentration of endothelin-1 in cubital Lein and cavernous body blood was lower than the 95% confidence intervals of patients with erectile dysfunction. The 20 patients with erectile dysfunction did not show significant variation in endothelin-1 concentration in cavernous body plasma collected 5 minutes and 30 minutes after prostaglandin E l injection (single t test for dependent samples). A close correlation was noted between intracavemous concentration of endotheh-1 at 5 minutes and 30 minutes
t Penipsula L+mratories, Belmont, $ Pepbde Insbtute, Osaka. Japan.
California.
1772
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION
+
TABLE2. Plasma level of endothelin-1 in diabetic and nondiabetic men with full or incomplete erection after intmcavernous injection of 10 pg. prostaglandin E l Mean Pg./MI. tSD)
-
n
W
4
I
+ w
0.8
0.6 0.4 0.2 C
A
B
FIG. 1. Plasma endothelin-1 concentration in cubital vein of 10 healthy subjects ( C ) ,10 nondiabetic (A) and 10 diabetic ( B )patients with erectile dysfunction. Values are mean plus or minus standard deviation. * <0.0005 versus C. + p <0.00001 versus A and versus C ANOVA r)ollowed by Fisher least significant difference test of repeated samples.
Diabetic pts.: No. pts. Endothelin-1 cubital vein basal Endothelin-1 cubital vein 30 min. after prostaglandin El Endothelin-1 intracavernous 5 min. after prostaglandin El Endothelin-1 intracavernous 30 min. after prostaglandin E l Nondiabetic pts.: No. pts. Endothelin-1 cubital basal Endothelin-1 cubital vein 30 min. after prostaglandin E l Endothelin-1 intracavernous 5 min. &r prostaglandin E l Endothelin-1 intracavernous 30 min. after prostaglandin E l Statistical analysis with Student's t
P Level
Full Erection
Incomplete Erection
4 1.7 (0.2) 2.1 (0.2)
6 1.8 (0.2) 1.9 (0.2)
0.47 0.16
2.2 (0.1)
2.0(0.1)
0.23
2.3 (0.2)
2.0 (0.3)
0.06
6
0.9 (0.4) 1.1 ( 0 . 5 )
4 1.4 10.5) 1.8 10.7)
0.11 0.13
1.0 (0.6)
1.5 (0.7)
0.24
1.1 (0.4)
1.6 (0.6)
0.21
test for independent samples.
patients with incomplete erection aRer prostaglandin E l injection had intracavernous levels of endothelin-1 in the high range, suggesting that patients with high intracavernous levels of endothelin-1 have more chance to show incomplete erection after intracavernous injection of prostaglandin E 1.
after prostaglandin E l injection (fig. 2) (r = 0.89, p <0.0001, y = 0.980 x + -0.066).Endothelin-1 concentration evaluated 30 minutes after prostaglandin E l injection did not show a significant difference between cavernous body and cubital DISCUSSION vein blood in the study groups (table 1). Our investigation showed that diabetic and nondiabetic Endothelin-1 in cubital vein and cavernous body blood of men with erectile dysfunction had significantly increased patients with full or incomplete erection after prostaglandin peripheral venous endothelin-1 level than normal men. InEl injection. Plasma concentration of endothelin-1 in cubital duction of corporeal smooth muscle relaxation by intracavvein and cavernous body blood was not significantly different ernous prostaglandin E l injection in men with erectile dysin diabetic and nondiabetic patients with full erection Comfunction was not associated with significant variation of pared to patients with incomplete erection achieved after endothelin-1 in cavernous body blood or peripheral vein injection of 10 pg. prostaglandin E l (table 2), suggesting that blood, and no difference was observed between levels of concentration of endothelin-1 in the cavernous body blood endothelin-1 in peripheral vein and cavernous blood in all and peripheral vein system was not predictive of penile erec- patients. Endothelin-1 was not measured in cavernous body tion efficacy induced by intracavernous injection of 10 pg. blood of normal men due t o the invasive nature of the prostaglandin E l . However, figure 2 shows that 8 of 10 procedure. Therefore, it is questionable whether levels of endothelin-1 reported in cavernous body blood of patients with erectile dysfunction were more elevated than in normal A men. However, 2 observations support this hypothesis. Cav'I 3 t ernous body blood endothelin-1 level in 3 patients affected by premature ejaculation and normal penis erection was lower than that observed in men with erectile dysfunction. Correlation was present between peripheral vein and cavernous body blood concentrations of endothelin-1 in all patients, 0 suggesting that elevated peptide level in peripheral vein h blood in men with erectile dysfunction was associated with 1 . 5 + elevated endothelin-1 concentration in cavernous body blood. Impaired endothelium dependent smooth muscle relaxation n 1 I has been demonstrated in cavernous tissue from diabetic men with impotence.2 The finding of elevated endothelin-1concentration in periphA eral venous blood and in cavernous body blood of diabetic men I I with erectile dysfunction suggests that impaired endothelium I dependent smooth muscle relaxation in corpus cavernosum* I0.5 1 1.5 2 2. s and in forearm resistance vessels of diabetic men4 could be due w E T - 1 IC 3 0 ' pomt P G E l (pg/ml) to the same endothelial dysfunction (reduced release) of endoRG.2. Relation of plasma endothelin-1 concentration in cavern- thelium derived relaxing factor as proposed by others2.4 and to ous body blood of 20 patients with erectile dysfunction, 5 minutes increased endothelin-1 release. Elevated plasma levels of after injection of 10 pg. prostaglandin E l in corpus cavernosum, to endothelin-1were reported in patients with atherosclerosis and plasma endothelin-1intracavemous concentration 30 minutes after might be related to diffuse endothelial cell dysfunction.12 Inprostaglandin E l iqjection. Dashed lines indicate predicted 95% confidence intervals,r = 0.89, p <0.0001, y = 0.980 x + -0.066. A, creased immunoreactivity for endothelin-1 in atherosclerotic patienta with full erection.0,patients with incomplete erection after carotid arteries compared to normal vessels and increased prostaglandin E l injection. plasma levels of endothelin-1were described in men with clin-
1773
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION
ical atherosclerosis.'2 Plasma and tissue endothelin-1 immunoreactivity was enhanced in early atherosclerosis induced by Our study revealed elevated circulating endothelin-1levels hsercholesterolemia in pigs, and coexisted with abnormal in diabetic and nondiabetic men with erectile dysfunction endothelium-dependent vasodilatation.13 Lncreased immunore- compared with normal men, and plasma endothelin-1 levels activity for endothelin-1 was shown in cutaneous vessels in men in cavernous body blood comparable to levels in peripheral with diabetes for less than 10 years compared with controls.14 vein blood. This result is indicative of endothelial dysfunction All of these findings suggest that elevated circulating that might contribute to erectile failure. Absence of a severe endothelin-1 levels may reflect local overproduction of peptide vasculogenic component of erectile failure suggests that infrom damaged endothelid cells with plasma spillover. creased plasma levels of endothelin-1 could be related to The target of endothelin-1 is neighboring muscle cell where early atherosclerotic disease. Results also suggest that evalendothelin-1 is maximally retained under pathological con- uation of endothelin-1 levels in peripheral vein blood is a ditions associated with increased plasma endothelin-1 lev- clinical marker of diffise endothelial disease manifested by els.':' Since endothelin-1 has properties as vasoconstrictofl erectile dysfunction. Concentration of endothelin-1 in cavernand growth factorlS acting through specific endothelin-A re- ous body blood and peripheral vein system was not predictive ceptors,16 we suggest that increased local endothelin-1 re- of penile erection efficacy induced by intracavernous injeclease during early atherosclerosis might contribute to patho- tion of 10 pg. prostaglandin E l . genesis of vascular changes and altered vascular tone present in clinical atherosclerosis.'3 Endothelin-1, produced by the endothelium in human corpus cavernosum, contracts corporeal smooth muscle acting through a receptor mediated REFERENCES effect.7 Elevated circulating levels of endothelin-1 suggest that erectile dysfunction in diabetic and nondiabetic men 1. Saenz de Tejada, I., Goldstein, I. and Krane, R. J.: Local control might be evidence of diffuse endothelial dysfunction. Excluof penile erection. Urol. Clin. N. Amer.. 15: 9, 1988. 2. Saenz de Tejada, I., Goldstein, I., Azadzoi, K. M., Krane, R. J. sion from the study of patients with severe vasculogenic and Cohen, R. A,: Impaired neurogenic and endotheliumerectile failure component suggests that endothelial dysfuncmediated relaxation of penile smooth muscle from diabetic tion might be related to initial atherosclerotic disease. men with impotence. New Engl. J. Med., 320: 1025, 1989. It is unlikely that a spillover of endothelin-1 exclusively 3. McCulloch, D. K., Campbell, I. W., Wu, F. C., Prescott, R. J. and from altered endothelial cells of corpus cavernosum might Clarke, B. F.: The prevalence of diabetic impotence. Diabetomaintain elevated circulating peptide levels, considering logia, 18: 279, 1980. rapid degradation of circulating peptide from lungs, kidney 4. Jhonstone, M. T., Creager, S. J., Scales, K M., Cusco, J. A., Lee, and liver,17 and catabolism of endothelin-1 by vascular B. K. and Creager, M. A.: Impaired endotheliumdependent smooth muscle cells.lS Altered relaxation of penile smooth vasodilation in patients with insulindependent diabetes mellitus. Circulation, 88:2510, 1993. muscle cells from diabetic men with erectile dysfunction has 5. Garcia, M. J., McNamara, P. M., Gordon, T. and h e l l , W. B.: been demonstrated.* Animal19 and human2 studies suggest Morbidity and mortality in diabetics in the Framingham popthat this result is due principally to impaired release of ulation. Sixteen year follow-up study. Diabetes, 23: 105. 1974. nitrous oxide from nonadrenergic noncholinergic nerve fibers 6. Saenz de Tejada, I., Blanco, R., Goldstein, I., Azadzoi, A., de las of corpus cavernosum.2 This is thought to be related to reMorenas, R., Krane, J. and Cohen, A.: Cholinergic neurotransduction of penile nitric oxide synthase,lSan enzyme activity mission in human corpus cavernosum. Responses to isolated normally present in human cavernous nerves and their tertissue. h e r . J. Physiol., 264: H459, 1988. minal endings within corporal erectile tissue and nerve plex7. Saenz de Tejada, I., Carson, M. P., De Las Morenas, A.. uses in the adventitia of deep cavernous arteries.2O Although Goldstein, I. and Traish, A. M.: Endothelin: localization, synthesis, activity, and receptor types in human penile corpus nitric oxide synthase has not been localized in endothelium cavernosum. h e r . J. Physiol., 261: H1078, 1991. lining vascular lacunae of the cavernous body,20 it has been 8. Rubanyi, G. M. and Boteho, L. H.: Endothelins. FASEB J., 5: shown that nitrous oxide or another closely related molecule 2713, 1991. acts as endothelium-derived relaxing substance in penile 9. Takahashi, K., Ghatei, M. A., Lam,H.-C., OHalloran, D. J. and smooth muscle.6 Bloom, S. R.: Elevated plasma endothelin in patients with Based on these findings and on results of our study, we diabetes mellitus. Diabetologia, 33:306, 1990. suggest that diabetes mellitus impairs endothelium depen- 10. Godschalk, M. F., Chen, J., Katz, P. G. and Mulligan, T.: Treatdent and neurogenic relaxation of penile smooth muscle of ment of erectile failure with prostaglandin El: a double-blind, diabetic men, due to impaired release of nitrous oxide from placebo-controlled, dose-response study. J. Urol., 161: 1530, nonadrenergic noncholinergic nerves and imbalance of a re1994. laxing nitrous oxide related molecule and a contracting 11. Hwang, T. I.-S.,Liu, P.-2. and Yang, C.-R.: Evaluation of penile dorsal arteries and deep arteries in arteriogenic impotence. endothelin-1 from endothelial cells. A study performed on J. Urol., 146.46, 1991. cavernous tissue from diabetic and nondiabetic men with erectile dysfunction showed in the former group an altered 12. Lerman, A., Edwards, B. S., Hallett, J. W., Heublein, D. M., Sandberg, S. M. and Burnett, J. C., Jr.: Circulating and tissue neuroendothelium and endothelium dependent relaxation endothelin immunoreactivity in advanced atherosclerosis. compared to the latter group.2 However, the integrity of the New Engl. J. Med., 326: 997, 1991. smooth muscle cell relaxing mechanism in normal men is not 13. Lerman, A., Webster, M. W., Chesebro, J. H., Edwards, W. D., known because cavernous tissue from normal men has not Wei, C.-M., Fuster, V. and Burnett, J. C., Jr.: Circulating and been evaluated. tissue endothelin immunoreactivity in hypercholesterolemic pigs. Circulation, 88: 2923, 1993. Although an altered neuro-dependent relaxation of corpus cavernosum cannot be ruled out in nondiabetic patients, the 14. Roperzi, G., Terenghi, G., Gu, X.-H., Poccia. G., Pasqua, R., Francavilla, S. and Polak, J. M.: Early increase precedes a finding of increased endothelin-1 concentration in the cubital depletion of endothelin-1 but not of Von Willebrand factor in vein of nondiabetic men with erectile dysfunction compared cutaneous microvessels of diabetic patients. A quantitative to normal men, and the finding of endothelin-1 concentration immunohistochemical study. J. Path., 175: 243, 1995. in cavernous blood of the same magnitude compared to cubi- 15. Bobik, A,, Grooms, A,, Millar, J. A,, Mitchell, A. and Grinpukel, tal vein is indicative of endothelial dysfunction in nondiaS.: Growth factor activity of endothelin on vascular smooth betic men with erectile failure. Increased endothelin-1 remuscle. Amer. J. Physiol., 268: C408, 1990. ' lease from altered endothelial cells in cavernous tissue might 16. Arai, H., Hori, S., Aramori, I., Ohkubo, H. and Nakanishi, S.: contribute to erectile dysfunction through its direct contractCloning and expression of a cDNA encoding an endothelin receptor. Nature, 348:730, 1990. h g effect on smooth muscle cells.? CONCLUSIONS
1774
ENDOTHELIN-1 IN ERECTILE DYSFUNCTION
17. Pernow, J., Hemsen, A., Lundberg, J. M.: Tissue specific distri-
bution, clearance and vascular effects of endothelin in the pig. Biochem. Biophys. Res. Comm., 161: 647, 1989. 18. Jackman, H. L., Moms, P. W., Deddish, P. A,, Skidgel, R. A. and Erdos, E. G.: Inactivation of endothelin 1 by deamidase (lysosoma1 protective protein). J. Biol. Chem., 261: 2872, 1992. 19. Vernet, D., Cai, L., Garban, H., Babbitt, M. L., Murray, F. T., Rajfer, J. and Gonzalez-Cadavid, N. F.: Reduction of penile
nitric oxide synthase in diabetic BFVWORdp (Type I ) and BBZ/ WORdp (Type 11) rats with erectile dyshnction. Endocrinology, 136 5709, 1995. 20. Burnett, A. L., Tillman, S. L., Chang, T. S. K, Epstein, J. I., Lowenstein, C. J., Bredt, D. S., Snyder, S. H. and Walsh, P. C.: Immunohistochemical localization of nitric oxide synthase in the autonomic innervation of the human penis. J. Urol., 150: 73. 1993.