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The aim of this study was to evaluate whether the sub-chronic systemic ethanol exposure has direct effect on cavernosal smooth muscle contractions induced by KCl (depolarizing) and phenylephrine (α1-receptor agonist), and the possible involvement of RhoA/Rho-kinase pathway. Sub-chronic systemic ethanol was applied to mice with inhalation route for 14 days. The blood levels in ethanol-treated mice averaged 121.2 ± 9.1 mg/dl. KCl (80 mM) and phenylephrine (10 nM-100 μM) induced sustained contractions in corpus corporal strips from sham-treated mice. Sub-chronic ethanol treatment reduced the contractions to KCl. However, phenylephrine-induced contractions were not affected by ethanol treatment. Rho-kinase inhibitor fasudil (50 μM) and Y-27632 (50 μM) inhibited contractions to KCl and phenylephrine in sham-treated mice. Ethanol treatment increased the inhibitory effect of Rho-kinase inhibitors on contractions to phenylephrine. The relaxations induced by fasudil (100 μM) and Y-27632 (500 μM) did not change in ethanol treatment group. In ethanol-treated group, the expression of RhoA decreased compared to sham-treated group. Also, ROCK1 expression was reduced by ethanol but not statically significant to sham-treated group; however, the expression of ROCK2 increased in ethanol group. From these findings, it seems that phenylephrine and KCl-induced contractions depends on RhoA/Rho-kinase-mediated Ca(2+) sensitization. Also, these results suggest that the ethanol treatment decreased the expression of RhoA, and the inhibitory effect of ethanol on KCl-induced contractions may be due to, at least in part, the inhibition of a RhoA/Rho-kinase in mouse corpus cavernosum.

We have studied the effect of an activator of soluble guanylate cyclase 4,7-dimethyl-1,2,5-oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide (FPTO) on the tone and nitrergic relaxation responses of mouse cavernous strips and compared FPTO to a known nitric oxide donor sodium nitroprusside. FPTO thiol-dependently generated nitric oxide measured by polarography and activated purified human soluble guanylate cyclase. FPTO and sodium nitroprusside relaxed the cavernous tissue in a concentration-dependent manner. A nitric-oxide synthase inhibitor N(omega)-nitro-L-arginine did not alter the relaxations to FPTO or sodium nitroprusside, whereas soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) suppressed relaxation to FPTO and sodium nitroprusside. Exogenously added thiols L-cysteine or dithiothreitol inhibited the relaxant responses to FPTO but not to sodium nitroprusside, whereas glutathione did not influence the responses to both agents. Thiol alkylation agent N-ethylmaleimide significantly enhanced FPTO-induced relaxation, and thiol-modifying agent diamide inhibited relaxation to FPTO. The potentiating effect of N-ethylmaleimide was neutralized by coadministration of N-ethylmaleimide with glutathione, L-cysteine, dithiothreitol, or ODQ. N-Ethylmaleimide but not diamide significantly inhibited relaxation induced by sodium nitroprusside. FPTO potently suppressed contraction to electrical field stimulation, which was prevented by glutathione or L-cysteine. In addition, FPTO did not affect relaxation produced by electrical field stimulation in phenylephrine-precontracted tissue. Our results show that FPTO can relax mouse corpus cavernosum and that the relaxant activity of this agent is thiol- and soluble guanylate cyclase-dependent. This effect could be potentiated by N-ethylmaleimide. FPTO does not potentiate nitrergic relaxation induced by electrical field stimulation.

We investigated whether bacterial lipopolysaccharide treatment causes any neuronal and vascular hyporeactivity in mouse cavernous tissue and also whether melatonin has any restorative effect on this possible neuronal and vascular hyporesponsiveness. Lipopolysaccharide treatment attenuated contractions in response to phenylephrine. Treatment with the inducible nitric oxide synthase inhibitor aminoguanidine or melatonin restored the hypocontractility of the cavernous smooth muscle to phenylephrine. Relaxant responses of corpus cavernosum precontracted by phenylephrine to acetylcholine or electrical field stimulation were significantly impaired in mice treated with bacterial lipopolysaccharide. Treatment with aminoguanidine or melatonin could prevent the impairment of the neuronal and endothelial relaxations. There was no significant difference between control and lipopolysaccharide-treated groups in the contractile response to high-dose KCl and in the relaxant response to papaverine. In conclusion, bacterial lipopolysaccharide treatment caused a neuronal and endothelial dysfunction in the mouse corpus cavernosum. A possible increased oxidative activity in the cavernous tissue may be a major reason for the impairment of relaxant responses and hypocontracility of tissue. The restorative effects of melatonin on this hyporeactivity may depend on its antioxidant properties and partly on its inhibitory action on the inducible nitric oxide synthase production., (Copyright 2004 S. Karger AG, Basel)

Acute effects of some divalent cations (Cd2+, Ni2+, Co2+, Zn2+, Mn2+ and Sn2+) were investigated on neurogenic and endothelium-dependent relaxations in the isolated mouse corpus cavernosum. Neither neurogenic nor endothelium-dependent relaxation was affected by cations at the concentrations used (up to 100 microM), except Cd2+. Although Cd2+ (20 and 40 microM) did not cause any significant alteration in the acetylcholine- (ACh) or sodium nitroprusside- (SNP) induced relaxation, it inhibited electrical field stimulation- (EFS) produced relaxation significantly. Zn2+ and selenium could not reverse this inhibitory action. Cd2+ did block the EFS-evoked guanethidine-sensitive contraction in the presence of N(G)-nitro-L-arginine. Elevation of external Ca2+ content significantly reduced the inhibitions due to Cd2+ on the EFS-induced relaxation and on the EFS-evoked guanethidine-sensitive contraction. In the Ca2+-omitted medium, EFS-induced relaxation disappeared, while acetylcholine-elicited relaxation resisted. Verapamil was ineffective on the relaxation produced by EFS or acetylcholine. However, it significantly diminished phenylephrine-induced contractions. These findings suggest that unlike other cations at the concentrations used in the present study, Cd2+ may have an effect on an external Ca2+-dependent mechanism at the neuronal level, and this effect may be responsible for its acute inhibitory action on the neurogenic relaxation in the mouse corpus cavernosum.

We studied the effect of vitamin E and sodium selenate treatment on the neurogenic and endothelium-dependent relaxation of isolated corpus cavernosum obtained from streptozotocin-induced diabetic mice. Relaxant responses of corpus cavernosum precontracted by phenylephrine to electrical field stimulation and to acetylcholine were significantly decreased in diabetic mice. There was no significant difference between diabetic and non-diabetic groups for the relaxant response of corpus cavernosum to sodium nitroprusside and papaverine. Treatment with sodium selenate, but not vitamin E, partially prevented the impairment of the neurogenic relaxation, whereas both had a significant, partial restorative action on endothelial dysfunction in corpus cavernosum obtained from diabetic groups. Neither agent exhibited a significant action on the relaxant responses of corpus cavernosum obtained from non-diabetic mice. A decrease in the sensitivity of the neurogenic impairment to antioxidant action may develop more rapidly than that of endothelial dysfunction in streptozotocin-induced diabetic mice.

We investigated whether Cd2+ intake (in drinking water, 15 ppm) for 30 days can affect the nitrergic relaxations of the mouse corpus cavernosum (CC) and whether Zn2+ (25 mg kg(-1) via a stomach tube at 48-h intervals) or sodium selenate (8 microg kg(-1) day(-1) intraperitoneally) has a restorative action on the impairment in the response. Relaxant responses of the CC obtained from Cd2+-treated mice to electrical field stimulation (neurogenic) or acetylcholine (endothelium dependent) were significantly inhibited. A partial restoration was observed in the nitrergic relaxation of the CC obtained from Zn2+- or sodium selenate-co-treated animals. Neither agent exhibited any significant action on the responses of the tissue from control mice. There was no significant difference between Cd2+-treated and control mice in respect of the relaxation amplitude induced by sodium nitroprusside or papaverine. These results suggest that Cd2+ intake may impair the nitrergic relaxation of the mouse CC, and, co-treatment with Zn2+ or sodium selenate may partially improve the nitrergic mechanisms in the tissue.