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Am J Physiol Cell Physiol 254: C423-C431, 1988;
0363-6143/88 $5.00
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AJP - Cell Physiology, Vol 254, Issue 3 C423-C431, Copyright © 1988 by American Physiological Society

ARTICLES

Beta-adrenergic actions on membrane electrical properties of dissociated smooth muscle cells

H. Yamaguchi, T. W. Honeyman and F. S. Fay
Department of Physiology, University of Massachusetts Medical School, Worcester 01605.

Studies were carried out to determine the effects of the beta-adrenergic agent, isoproterenol (ISO), on membrane electrical properties in single smooth muscle cells enzymatically dispersed from toad stomach. In cells bathed in buffer of physiological composition, the average resting potential was -56.4 +/- 1.4 mV (mean +/- SE, n = 35). The dominant effect of exposure to ISO was hyperpolarization. The hyperpolarization was apparent in all cells studied and averaged 11.6 +/- 1.2 mV (n = 27). In the majority of the cells, hyperpolarization was accompanied by a decreased input resistance (Rin). Often the change in resistance appeared to lag behind the change in membrane potential. The lack of coincident changes in membrane potential and resistance may reflect a superposition of the outward rectification properties of the membrane on beta-adrenergic-induced increases in ionic conductance. In about half of the cells, an initial small depolarization (3.1 +/- 0.3 mV, n = 14) was accompanied by a small but distinct increase in Rin (12 +/- 2.5%). When membrane potential was made more negative than the estimated equilibrium potential for K+ (EK) by injection of current, ISO also produced biphasic effects, an initial hyperpolarization which reversed to a sustained depolarization to a value (-90 mV) near the estimated EK. The hyperpolarization by ISO could be diminished in a time-dependent manner by previous exposure to ouabain. The inhibition by ouabain, however, appeared to be a fortuitous result of glycoside-induced positive shifts in EK. These observations indicate that the dominant electrophysiological effect of beta-adrenergic stimuli is to hyperpolarize the cell membrane.(ABSTRACT TRUNCATED AT 250 WORDS)


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H. KURIYAMA, K. KITAMURA, T. ITOH, and R. INOUE
Physiological Features of Visceral Smooth Muscle Cells, With Special Reference to Receptors and Ion Channels
Physiol Rev, July 1, 1998; 78(3): 811 - 920.
[Abstract] [Full Text] [PDF]


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