Regulation Of L-type Calcium Channel Currents In Isolated Rat Ventricular Myocytes

We investigated the effect of phenylarsine oxide (PAO), one of sulfhydryl group (-SH) oxidizing agents, on the L-type calcium channel currents (1^ L) in isolated ventricular myocytes by using the whole-cell voltage clamp technique. 10<, 20> 100 ujnol/L PAO suppressed the basal ICa,Lby44?3%(?6, P<0.01), 59 ?% (n=6, P L amphtude by 51.4 ?7.9% (?4, PO.01). These results indicate that the changes in osmolarity of rat ventricular myocytes can modulate the function of L-type calcium channel. CONCLUSIONPAO inhibits the basal and cAMP/PKA activated 1^ L in rat ventricular myocytes. The inhibition maybe not due to the inhibition of cAMP/PKA signaling pathways but probably is an oxidative effect directly on the -SH of the Ca2+ channels. The changes in osmolarity of rat ventricular myocytes can modulate the function of L-type calcium channel. Lowering osmolarity to 220 mOsm/kg H20 did not significantly increased the amplitude of the IC^L, but the rundown of the current was slow. Hyperotonic solution (410 mOsm/kg H2O) reduced IC^L amplitude.