Protein kinase A increases availability of calcium channels in smooth muscle cells from guinea pig basilar artery.

Abstract

We studied single Ca2+ channels in smooth muscle cells from the basilar artery of the guinea pig using conventional patch-clamp techniques. With 40 mM or 90 mM Ba2+ as the charge carrier, a 23-pS inward current channel was observed in 46/187 cell-attached patches studied without the dihydropyridine, BAY K8644, in the pipette solution. At 0 mV, this channel exhibited short and long openings with time constants of 1.03 and 3.65 ms, respectively. The probability of channel opening was voltage dependent with half-activation occurring at +9.9 mV. In 14/26 patches tested, addition of 8-bromo-cyclic adenosine monophosphate (8-Br-cAMP) to the bath increased the probability of opening at -10 mV by a factor of 2.6, from 0.0272 +/- 0.0429 to 0.0695 +/- 0.0788 (P < 0.01, paired t-test). Mean data from five patches fit to a Boltzmann function indicated that at positive potentials, the probability of opening increased by a factor of 1.7, from 0.352 to 0.600, whereas the voltage dependence, the number of channels, the number of open states, the time constants of the open states, and the proportion of time spent in each open state were unchanged. When BAY K8644 was added to the pipette solution, the 23-pS channel was observed in nearly all patches (62/66), but the voltage dependence of activation was shifted -15.3 mV compared to control. In some patches studied with 90 mM Ba2+, a 9-pS inward current channel also was observed and its activity also was increased significantly by 8-Br-cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)