Fh. Chen et al., ADENYLYL-CYCLASE INTEGRATES MULTIPLE G-PROTEIN SIGNALS TO MODULATE CALCIUM CURRENTS IN NEONATAL RABBIT HEART, Biochemical and biophysical research communications, 216(1), 1995, pp. 190-197
We investigated the effects of added beta gamma subunits of G proteins
(G beta gamma) on beta-adrenergic responsiveness of transmembrane Ca2
+ currents (I-Ca) in ventricular myocytes from neonatal rabbits. G bet
a(1 gamma 1) purified from retinal rods was dialyzed into cells via th
e voltage clamp micro-electrode. Stimulation of I-Ca by isoproterenol
was not affected by added intracellular G beta(1 gamma 1) or by carbac
hol alone but was completely blocked by combined G beta(1 gamma 1) and
carbachol. Pretreatment of cells with pertussis toxin or temporal sep
aration of carbachol and isoproterenol allowed stimulation of I-Ca by
isoproterenol in cells dialyzed with G beta(1 gamma 1). Carbachol and
G beta(1 gamma)1 together also did not prevent stimulation of I-Ca by
dibutyryl-cyclic AMP. Thus, rather than simply inactivating G(s) alpha
by mass action, G beta(1 gamma 1) acts in concert with carbachol to i
nhibit isoproterenol stimulation of I-Ca. (C) 1995 Academic Press, Inc
.