Effects of ethanol on the tonicity of corporal tissue and the intracellular Ca2+ concentration of human corporal smooth muscle cells.

Heavy alcohol consumption is associated with an increased risk of erectile dysfunction (ED); however, the acute effects of ethanol (EtOH) on penile tissue are not fully understood. We sought to investigate the effects of EtOH on corporal tissue tonicity, as well as the intracellular Ca(2+) concentration ([Ca(2+)](i)) and potassium channel activity of corporal smooth muscle. Strips of corpus cavernosum (CC) from rabbits were mounted in organ baths for isometric tension studies. Electrical field stimulation (EFS) was applied to strips precontracted with 10 μmol L(-1) phenylephrine as a control. EtOH was then added to the organ bath and incubated before EFS. The [Ca(2+)](i) levels were monitored by the ratio of fura-2 fluorescence intensities using the fura-2 loading method. Single-channel and whole-cell currents were recorded by the conventional patch-clamp technique in short-term cultured smooth muscle cells from human CC tissue. The corpus cavernosal relaxant response of EFS was decreased in proportion to the concentration of EtOH. EtOH induced a sustained increase in [Ca(2+)](i) in a dose-dependent manner, Extracellular application of EtOH significantly increased whole-cell K(+) currents in a concentration-dependent manner (P < 0.05). EtOH also increased the open probability in cell-attached patches; however, in inside-out patches, the application of EtOH to the intracellular aspect of the patches induced slight inhibition of Ca(2+)-activated potassium channel (KCa) activity. EtOH caused a dose-dependent increase in cavernosal tension by alterations to [Ca(2+)](i). Although EtOH did not affect KCa channels directly, it increased the channel activity by increasing [Ca(2+)](i). The increased corpus cavernosal tone caused by EtOH might be one of the mechanisms of ED after heavy drinking.