Influence of Potassium Ion Permeability on NE-Induced Excitation/Contraction Coupling in Vascular Smooth Muscle

Abstract

The sensitivity of rabbit superior mesenteric artery contractions to the calcium antagonist D600 was studied. Contractions were elicited through receptor activation by Norepinephrine (NE) or by non-specific depolarization by an 80 mM-K+-PSS. Results indicate that smooth muscle membranes are more sensitive to D600 under 80 mM-K+-PSS depolarization than under NE induced contractions. This suggests that there is some distinction between the mechanisms of both muscle activation techniques. Both NE-sensitive Calcium release and influx were analyzed under the influence of altered potassium concentration, Na/K ATP-ase inhibition with Ouabain, and the potassium channel blocker, Tetraethylammonium (TEA). Results indicate that with partial membrane depolarization, caused by the above manipulations, several observations can be made. Sensitivity to D600 relaxations of NE-induced contractions increases, along with an increase in the intracellular calcium release component of the smooth muscle contraction.