AJP - Renal Physiology, Vol 253, Issue 4 636-F641, Copyright © 1987 by American Physiological Society

ARTICLES

Electrophysiological analysis of beta-receptor stimulation in salamander proximal tubules

N. S. Morgunov
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada.

Electrophysiological response to isoproterenol stimulation was studied in isolated perfused salamander proximal tubules. The addition of 10(-5) M isoproterenol to the bath superfusate depolarized both the cell membrane, and transepithelial potentials by 2.2 +/- 0.2 and 0.31 +/- 0.04 mV, respectively (P less than 0.01, n = 35) and significantly reduced the apical-to-basolateral membrane resistance ratio by 30% (P less than 0.01, n = 7) from a control value of 3.7 +/- 0.6. These responses were blocked by 10(-6) M propranolol but not mimicked by 10(-4) M adenosine 3',5'-cyclic monophosphate. Qualitatively similar effects were observed with 10(-3) and 10(-7) M isoproterenol. Further characterization of the 10(-5) M isoproterenol response revealed 1) a 50% reduction in the response following the removal of organic substrates from the luminal perfusate, 2) an absolute requirement for sodium, and 3) an absolute requirement for a functioning basolateral Na+-K+-ATPase. The data suggest that beta-receptor stimulation may increase sodium reabsorption by activating sodium cotransport systems.

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