[Single Ca2+-activated K+-channels in cultured kidney cells Vero]

Using the patch voltage-clamp method ("inside-out" mode) properties of single Ca(2+)-activated K+ channels in cultured kidney cell Vero were studied. Two types of kinetically distinct channels (fast and slow) were found. The fast and slow channels differ by single channel conductance, kinetic parameters, characteristics of interaction with Ca2+, and voltage dependency degree of the kinetics parameters, but are similar in ionic selectivity in respect to monovalent cations. It was found that the channel conductance varies from patch to patch between 140 and 230 pS. Average values of single channel open duration and an apparent dissociation constant were correlated with the single channel conductance. The relationship was found: the more the conductance the lesser the open time duration and more the dissociation constant. The data suggest that there is almost continuous spectrum of subtypes of the Ca(2+)-activated K+ channels, the fast and slow channels being extreme groups of this spectrum. The data are regarded from the viewpoint of the clustery hypothesis.