Comparative studies of the maxi-K (K-Ca) channel in freshly isolated myocytes of human and rat corpora

Patch clamp techniques in freshly isolated myocytes from human corpora have documented that the large conductance calcium-sensitive K channel (K-Ca) s ubtype represents an important convergence point for the modulation of corp oral smooth muscle tone, and therefore, erectile capacity, Other recent stu dies indicate a similar role for the K-Ca channel in the modulation of smoo th muscle tone in the rat penis, Therefore, the explicit aim of this invest igation was to evaluate and compare the characteristics of the K-Ca channel subtype present in freshly isolated myocytes from rat and human corpora, I n short, myocytes isolated from rat and human corpora retain their characte ristic morphology and contractility in vitro, as evidenced by light microsc opic studies of their respective responses to activation of the alpha(1)-ad renergic receptor subtype by phenylephrine (PE). Large conductance K+ curre nts commensurate with the presence of the K-Ca channel were readily apparen t in myocytes from both preparations. I-V curves constructed from cell-atta ched patches utilizing symmetric KCI solutions revealed the presence of a s ingle channel slope conductance of approximate to 200 pS for both rat and h uman myocytes, 1 mM TEA applied in the bath solution reversibly diminished whole cell outward K+ currents by approximate to 50%, and also blocked the unitary Kc, channel activity observed in the outside-out patch mode, Additi on of 2 mM 8-bromo-cAMP elicited a TEA-sensitive (1 mM) approximate to 2-3 fold increase in the magnitude of the whole cell outward K+ currents in rat myocytes, Taken together, these data confirm and extend previous observati ons and provide strong evidence that the rat corporal smooth muscle K-Ca ch annel has many similarities to its counterpart in the human penis.