PT  - JOURNAL ARTICLE
AU  - Wilde, D W
TI  - Isoflurane reduces Ca++ channel current and accelerates current decay in guinea pig portal vein smooth muscle cells.
DP  - 1994 Dec 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1159--1166
VI  - 271
IP  - 3
4099  - http://jpet.aspetjournals.org/content/271/3/1159.short
4100  - http://jpet.aspetjournals.org/content/271/3/1159.full
SO  - J Pharmacol Exp Ther1994 Dec 01; 271
AB  - The volatile anesthetic isoflurane (ISO) can exert significant inhibitory effects on hemodynamics and organ perfusion. It was hypothesized that venodilation during ISO exposure was mediated through a reduction in inward Ca++ channel current. By using the whole cell mode of single cell patch clamp technique, the action of ISO on L-type Ca++ channel current was examined. ISO caused a concentration-dependent reduction in maximal Ca++ channel current and shifted the current activation to more negative potentials. ISO, 3%, shifted the voltage for half-maximal channel inactivation from -21.9 to -33.4 mV. Measurement of time constants for inward current activation and inactivation revealed that the inactivation phase exhibited a concentration-dependent reduction over the range of 0.36 to 3% ISO. The decrease in the inactivation time constant is consistent with accelerated inactivation of the L-channel current. Estimated binding constants for ISO to resting or inactivated channels suggest absence of state-dependent inhibition of channel conductance. The venodilatory effects of ISO are due in part to limitation of Ca++ influx which may secondarily affect Ca(++)-dependent mechanisms such as the outward Ca(++)-activated K+ channel population. Reduction in current by ISO may occur through receptor-independent mechanisms and may involve perturbation of the sarcolemmal lipid bilayer.