[Involvement of voltge dependent potassium channels in rabbit corpus cavernosum responses to oxidative stress]

Previously we have demonstrated that oxidative stress produces a complex response of the rabbit corporal smooth muscle cells consisting of transient relaxation followed by contraction. We used 4-AP and TEA, selective blockers for voltage- and Ca(2+)-dependent K+ channels to investigate possible contribution of these channels in maintaining of basal cavernosal tone as well as in mediating of contractile response caused by oxidative stress. TEA in concentration of 1 mmol/l caused contraction of corporal smooth muscle. Application of hydrogen peroxide (H2O2) in the presence of TEA caused contraction similar to that in control conditions. This argues against involvement of Ca(2+)-dependent K+ channels in contractile response caused by oxidative stress. On the other hand, contractile response on inhibition of Ca(2+)-dependent K+ channels suggests their contribution in maintaining of corporal tone. 4-AP in concentration of 5 mmol/l caused contraction resembling that, evoked by TEA. Thus, voltage-dependent similar to Ca(2+)-dependent K+ channels contribute to corporal tone. In the presence of 4-AP H2O2 induced contraction was essentially decreased. The most probable explanation of this result is that population of channels modulated by 4-AP and H2O2 is common for both factors. We previously reported that H2O2 induced contraction could be inhibited by indometacine. Together these results suggest, that H2O2 induced contraction could be a result of inhibition of 4-AP-sensitive voltage-dependent K+ channels that is mediated by metabolite products of arachinoide acid via cyclooxigenase pathway.