Consequences of chronic ethanol consumption on the reactivity and expression of components of the endothelinergic system in the rat corpus cavernosum.

LN Leite1, H Côco1, R Lacchini1, JE Tanus-Santos1, EC Carnio2, R Queiroz3, AM De Oliveira3, CR Tirapelli2. 1University of São Paulo, Department of Pharmacology School of Medicine of Ribeirão Preto 14049 900, Brazil, 2University of São Paulo, College of Nursing of Ribeirão Preto 14040 902, Brazil, 3University of São Paulo, Faculty of Pharmaceutical Sciences of Ribeirão Preto 14040 903, Brazil

Introduction: Endothelin-1 (ET-1) is a vasoconstrictor peptide that plays an important role in controlling the tone of the cavernous body. However, it has been demonstrated that this peptide is also involved in erectile dysfunction (ED) associated with diabetes mellitus and hypertension. Ethanol consumption increases plasma levels of ET-1 and the contractile response to this peptide in vascular tissues. This study aimed to investigate the cellular and functional consequences of chronic ethanol consumption on the endothelinergic system in penile circulation as well as the mediators involved in this response. Methods: Male Wistar rats were treated with ethanol (20% vol/vol) for 6 weeks. Reactivity experiments were performed on isolated cavernosal smooth muscle (CSM). Cumulative concentration-response curves for phenylephrine (PhE), endothelin-1 (ET-1), sodium nitroprusside (SNP), acetylcholine (ACh) and IRL-1620, a selective ETB agonist, were performed. Nitrate levels were measured in plasma and supernatants from total CSM homogenates. mRNA for pre-pro-ET-1, ETA and ETB receptors, inducible NO synthase (iNOS), neuronal NO synthase (nNOS) and endothelial NO synthase (eNOS) was assessed by RQ-PCR. Plasma ET-1 was measured by enzyme immunoassay (EIA). Results: Blood ethanol levels in the ethanol-treated rats averaged (1.91 ± 0.21 mg/ml n=11). Chronic ethanol consumption increased plasma ET-1 levels. Body weight of the rats before beginning the treatment averaged (284 ± 5g) in control group and (289 ± 3g) in ethanol group. The treatment for 6 weeks reduced the body weight of the rats from ethanol group (477 ± 10g) when compared to control group (592 ± 9g) (P<0.05, ANOVA). Our findings show that phenylephrine-induced contraction in isolated CSM strips was not altered after treatment with ethanol. On the other hand, ET-1-induced contraction was significantly higher in cavernosal strips from ethanol-treated rats (32 ± 2.8% KCl 120mM; n=7) when compared to control (21.5 ± 1.5% KCl 120mM; n=6) (P<0.05, Student’s t test). Chronic ethanol consumption reduced the relaxation induced by acetylcholine (28.4 ± 1.4%, n=7) in the rat CSM when compared to control group (39.4 ± 1.4%, n=10) (P<0.05, Student’s t test). IRL-1620 and sodium nitroprusside-induced relaxation were not affected by ethanol consumption. It was found that chronic ethanol consumption did not alter mRNA levels for ETA or ETB receptors, pre-pro-ET-1, iNOS, nNOS and eNOS. Finally, ethanol consumption reduced nitrate plasma levels. Conclusion: The present findings demonstrate that there is a link between chronic ethanol consumption and alterations on the endothelinergic pathway in the penile circulation. Financial Support: CAPES, FAPESP.