Objectives: To evaluate non-genomic effects of testosterone and dihydrotestosterone (DHT) on isolated human cavernosal arteries (HCA) and corpus cavernosum (HCC) using organ-bath studies and radio-immunoassays (RIA), as non-genomic effects of androgens are reported for vascular smooth musculature and there is evidence that the relaxant response involves a modulation of cyclic nucleotide tissue levels.
Materials and methods: The relaxation induced by the cumulative addition of testosterone and DHT (0.01-10 microm) was studied using circular segments of HCA and strip preparations of HCC. To evaluate the effects of testosterone and DHT on tissue levels of cAMP and cGMP, specimens were exposed to increasing concentrations of the hormones. Forskolin and sodium nitroprusside (SNP) served as reference compounds.
Results: Testosterone and DHT dose-dependently reversed the noradrenaline-induced tension of vascular segments and HCC strips. At the maximum concentration, testosterone and DHT reduced the mean (sd) tension to 79.8 (4.43)% and 83.9 (10.94)%, respectively. SNP and forskolin significantly stimulated the production of cGMP and cAMP. No effects of testosterone and DHT on cGMP and cAMP levels were detected.
Conclusion: Rapid androgen-induced relaxation of HCA and HCC occurs via non-genomic mechanisms. In penile erectile tissue, non-genomic relaxant effects of testosterone and DHT are not mediated via modulation of cyclic nucleotide tissue levels. Additional studies are required to establish if non-genomic relaxant effects are important in ensuring a basal level of perfusion to maintain overall penile function.