The Effects of beta-adrenocreptor Stimulation on the Maxi-K+ Channels in Human Corporal Smooth Muscle Cells

Lee, Sung Won

Abstract

PURPOSE: beta-adrenoceptors have been demonstrated in human corporal smooth muscles by the receptor binding assays, and have been known to elicit relaxation of the precontracted corporal tissues. Despite these findings, it is not clear whether the beta-adrenoceptors have any role in the control of penile erection. Potassium channels play an important role in the physiology of the corporal smooth muscle. The maxi-K+ channel subtypes are thought to be the most physiologically relevant K+ channels expressed in this tissue. The goal of this study was to clarify the contribution of the beta-adrenoceptors to the modulation of the corporal smooth muscle tone.
MATERIALS AND METHODS
Patch-clamp technique was applied to the cultured human corporal smooth muscle cells.
RESULTS
Maxi-K+ channel was activated by the application of the beta-adrenoceptor stimulator, isoproterenol (ISO). ISO increased the open probability (nP0) by 512+/-53% and the mean open time by 214+/-12% in the cell-attached patch recording. The whole cell patch recording indicated that the application of ISO in the bath solution increased the peak amplitude of the whole cell outward K+-current during the step depolarization (from -70 to + 130 mV). The presence of a specific protein kinase A inhibitor (PKI) in the pipette tip suppressed the ISO-induced increase of the whole cell outward K+-current.
CONCLUSIONS
These studies showed that the beta-adrenoceptor activation contributed to the modulation of the corporal smooth muscle tone by activating the potassium channels, and moreover, that the activation of the potassium channels by the beta-adrenoceptors was related to the protein kinase A pathway.