Ca 2+ -Sensitive K + Channel in Aortic Smooth Muscle of Rats

Abstract

Abstract

We measured K⁺ channel activity in inside-out patches of cell membrane from aortic vascular smooth muscle cultured (Passages 1–3) from Wistar, Wistar-Kyoto, and spontaneously hypertensive rats (SHR). With [Ca²⁺]_i between 25 and 100 nm and 150 mm K⁺ on both sides of the membrane, the conductance of this channel was 55 ± 7 pS (slope of current-voltage curve through 0 mV) and the current was outwardly rectified. There was no difference in single-channel conductance among the three rat strains. Increasing negative holding voltages or increasing [Ca²⁺]_i, increased the probability of this type channel being open (Np_o; P < 0.01); SHR had a larger NP_o (P < 0.01). Compared with cells from Wistar and Wistar-Kyoto, cells from SHR also had the longest mean open time. The increased NP_o and mean open time we observed in this K⁺ channel of cells from SHR could contribute, at least in part, to the increased membrane K⁺ permeability, reported previously.