AJP - Heart and Circulatory Physiology, Vol 242, Issue 5 900-H906, Copyright © 1982 by American Physiological Society
Membrane properties of smooth muscle cells in pulmonary arteries of the rat
H. Suzuki and B. M. Twarog
Electrical properties of the membrane of smooth muscle cells in the rat
main pulmonary artery (MPA) and a small pulmonary artery (SPA) were
compared. MPA and SPA differed in several important respects, suggesting
characteristic quantitative and qualitative differences in membrane
properties. 1) Resting membrane potentials were similar in both (MPA 52.2
+/- 1.3 mV; SPA 51.5 +/- 1.7 mV). The cells displayed no spontaneous
electrical activity. The muscle layers in both MPA and SPA showed cablelike
properties; a graded local response to outward current pulses was observed,
but no action potentials were evoked. 2) Tetraethylammonium chloride (TEA,
1-5 mM) depolarized, increased membrane resistance, and suppressed
rectification in MPA. TEA strongly depolarized SPA and contraction ensued.
3) The maximum membrane depolarization produced by a 10-fold increase in
extracellular [K+] was 48 mV in MPA and 47 mV in SPA. In K+-free solution
gradual depolarization was observed in SPA, but the membrane potential in
MPA was not modified. Restoration of K+-containing solution produced
equivalent hyperpolarization in both tissues, indicating a similar degree
of stimulation of electrogenic Na+-K+ pumping. 4) A Na+-deficient solution
did not affect the membrane potential in MPA but depolarized SPA.
