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.