Protective effects of resveratrol treatment on hypercholesterolemic rabbit corpus cavernosum tissue

N Murat1, O Kizer2, AS Evcim1, P Korhan3, O Demir2, A Kefi2, N Atabey3, S Gidener1, AA Esen2. 1Dokuz Eylul University School of Medicine, Department of Pharmacology,35340, Izmir, Turkey, 2Dokuz Eylul University School of Medicine, Department of Urology, 35340,Izmir, Turkey, 3Dokuz Eylul University School of Medicine, Department of Medical Biology and Genetics, 35340,Izmir, Turkey

Impaired release and reduced bioavailability of nitric oxide are the hallmark for endothelial as well as erectile dysfunction. Hypercholesterolemia is known to be a risk for endothelial dysfunction that results in vasculogenic erectile dysfunction. Our aim was to investigate whether treatment with resveratrol has potential to protect corpora cavernosa (CC) of the penis from the effect of hypercholesterolemia and its involment with eNOS regulation.

Adult male New Zealand rabbits (BW 2500-3000g) were divided into three groups as; control (Group-1, n=7), cholesterol-fed animals (Group-2, n=7), and cholesterol-fed with 8mg/kg/day resveratrol treatment (Group-3, n=7). In preliminary study animals were treated with 4 mg/kg/day, 6 mg/kg/day and 8 mg/kg/day dose of resveratrol. 8mg/kg/day resveratrol treatment proved Ach-mediated relaxation responses significantly higher than the other dose treatments. All animals except control were fed with 2% a/a cholesterol diet for 6 weeks. Resveratrol was administered with drinking water for 6 weeks. The animals were anesthetized with 60mgkg– 1 thiopental and killed by exsanguination from the common carotid in the 7th week of the experiment. Corpus cavenosum was rapidly removed and placed in Krebs–Henseleit solution. Adherent fat and surrounding tissue were cleaned off and were cut into 3x3x4mm3 strips for CC.

Total cholesterol, HDL and LDL levels were measured in all animals at the beginning and at the end of the study. Endothelial functions in CC was assessed by isolated organ bath. Cumulative doses of acetylcholine (Ach) (10-8 -10-5 M) were applied to the tissues precontracted with 3x10-6 M phenylephrine (Phe) in the presence and absence of L-nitro-N-arginin metilester (LNAME). 3x10-5M LNAME was applied 30 minute before Phe administration. Isometric tensions were recorded with an amplifier system (MP30 Biopac systems Inc., Santa Barbara, CA, USA) on a computer by using Biopac computer program. Regulation of eNOS was evaluated at mRNA and protein level. The statistical significance of differences of groups were analyzed by one-way ANOVA and student’s t-test. P-values <0.05 were considered significant

Feeding rabbits with cholesterol-diet for 6 weeks resulted in hypercholesterolemia confirmed by blood measurements. Resveratrol administration to the cholesterol-fed animals for 6 weeks did not restore increased blood cholesterol levels. While Ach-induced relaxation responses were significantly reduced in group-2 compared to control (29,09±3,95% vs 48,58±4,16%, p<0.01), resveratrol administration augmented these responses (53,01±3.88%). Parallel to the improvements in smooth muscle relaxation responses, feeding with high dose cholesterol and resveratrol treatment had significant effect on eNOS activation.

This study has demonstrated that resveratrol administration in hypercholesterolemia-induced rabbits for 6 weeks could dose-dependently protect corpora cavernosal smooth muscle relaxation of the penis without affecting blood lipid levels, resulting in preserved endothelial and erectile function. We suggest that the protective effects of resveratrol might be mediated by the NO pathway.

Key words

Resveratrol, endothelial dysfunction, hypercholesterolemia, corpus cavernosum