The effects of interleukin-6 on the contraction and relaxation responses of the cavernous smooth muscle from rats

The purpose of this study is to elucidate the effect of IL-6 on the vasomotor reactivity of the corpus cavernosum of the rats. The strips were either left untreated or treated with 1 ng/ml of IL-6 for 60 min. By increasing concentrations of phenylephrine, acetylcholine, or sodium nitroprusside, we assessed concentration-contraction or relaxation responses. The IL-6-treated strips were incubated for 30 min with or without l-NAME (NW-nitro-l-arginine methyl ester), l-arginine, indomethacin, BQ-123 (an endothelin receptor A inhibitor), or SQ 29,548 (a thromboxane A2 [TXA2] receptor blocker), and the effects on phenylephrine-induced contraction or acetylcholine-induced relaxation of phenylephrine-induced contraction were measured. The contractile responses to phenylephrine were significantly enhanced in the IL-6-treated strips, compared with the IL-6-nontreated strips, and the relaxation responses to acetylcholine were significantly inhibited in the IL-6-treated group compared with the IL-6-nontreated group. But after endothelial denudation, there was no difference between the IL-6-treated strips and the IL-6-nontreated strips on the contraction-relaxation responses to phenylephrine or acetylcholine. The relaxation responses to sodium nitroprusside were not inhibited in both groups. l-NAME completely inhibited the relaxation response to acetylcholine in the IL-6-treated strips, as well as the IL-6-nontreated strips. Indomethacin and SQ 29,548 significantly inhibited the increased contractile responses to phenylephrine in the IL-6-treated strips. But BQ 123 rarely affected the same responses. l-arginine reversed the inhibited relaxation responses to acetylcholine in the IL-6-treated strips. Therefore, IL-6 inhibits endothelium-dependent, NO-mediated relaxation and also enhances α1-adrenergic receptor-mediated contraction via an endothelium-dependent TXA2-mediated mechanism in the corpus cavernosum of the rat.