AJP - Renal Physiology, Vol 258, Issue 6 1497-F1503, Copyright © 1990 by American Physiological Society

ARTICLES

Basolateral cell membrane Ca-Na exchange in single rabbit connecting tubules

J. E. Bourdeau and K. Lau
Department of Medicine, Michael Reese Hospital and Medical Center, Chicago, Illinois 60616.

Studies of cortical proximal nephrons and plasma membrane vesicles suggest that a Ca-Na exchanger regulates intracellular Ca2+ concentration ([Ca2+]i) in renal tubular cells. We tested this hypothesis in isolated perfused rabbit connecting segments by measuring [Ca2+]i with fura-2. Within 2 min of replacing bath NaCl with mannitol, [Ca2+]i rose from a base line of approximately 100 nM to a peak of approximately 650 nM, then declined to a plateau of approximately 500 nM for approximately 5 min before rising to a second peak of approximately 600 nM. [Ca2+]i returned toward base line after restoring bath NaCl. Substitution of choline Cl or tetraethylammonium chloride for bath NaCl reproduced the rise in [Ca2+]i, implicating the Na+ as the mediator. Selective bath (but not lumen) Ca removal or lumen Na deletion virtually abolished these effects, suggesting that bath Na deletion causes peritubular Ca influx by a process that depends on lumen Na. Lumen Na removal lowered, whereas its repletion increased, [Ca2+]i. Smaller increments in [Ca2+]i were produced by raising lumen [Na] from 0 to 35-55 mM or from 20 to 120 mM, but not from 55 to 150 mM. Clamping bath [Ca] at approximately 100 nM abolished the rise in [Ca2+]i produced by lumen Na, corroborating the role of peritubular Ca. These results suggest a Ca influx across the basolateral membrane that is driven by a cell-to-bath [Na] gradient and that can be activated by changes in lumen [Na]. We propose that this process, in part, regulates [Ca2+]i in the rabbit connecting tubule.

This article has been cited by other articles:

				S. N. Kip and E. E. Strehler Characterization of PMCA isoforms and their contribution to transcellular Ca2+ flux in MDCK cells Am J Physiol Renal Physiol, January 1, 2003; 284(1): F122 - F132. [Abstract] [Full Text] [PDF]

				R. F. Reilly and D. H. Ellison Mammalian Distal Tubule: Physiology, Pathophysiology, and Molecular Anatomy Physiol Rev, January 1, 2000; 80(1): 277 - 313. [Abstract] [Full Text] [PDF]

				M. P. Blaustein and W. J. Lederer Sodium/Calcium Exchange: Its Physiological Implications Physiol Rev, July 1, 1999; 79(3): 763 - 854. [Abstract] [Full Text] [PDF]