G-PROTEIN-MEDIATED SUPPRESSION OF L-TYPE CA2+ CURRENT BY INTERLEUKIN-1-BETA IN CULTURED RAT VENTRICULAR MYOCYTES

The effect and possible signal transduction pathway of interleukin-1 beta (IL-1 beta) on the L-type Ca2+ current (I-Ca,I-L) in cultured adult rat ventricular myocytes were examined using whole cell patch-clamp techniques. When myocytes were internally dialyzed with a solution containing GTP, IL-1 beta caused a concentration-dependent decrease in the peak I-Ca,I-L (Ba2+ as the charge carrier). IL-1 beta did not significantly alter the voltage dependence of the peak I-Ca,I-L nor the steady-state inactivation and activation, but did slightly slow the rate of inactivation. In myocytes dialyzed with solutions without GTP or including guanosine 5'-O-(2-thiodiphosphate) to replace GTP, IL-1 beta had no effect on I-Ca,I-L. In contrast, when guanosine 5'-O-(3-thiotriphosphate) was used to replace GTP, the suppression of I-Ca,I-L induced by IL-1 beta remained. Preincubation of myocytes with pertussis toxin (PTX), which completely abolished the acetylcholine effect on isoproterenol-stimulated I-Ca,I-L, had no effect on the inhibitory action of IL-1 beta on I-Ca,I-L. We conclude that in cultured rat ventricular myocytes, IL-1 beta suppresses I-Ca,I-L via a PTX-insensitive G protein.