Role of membrane - permeable ions in renin secretion by renal juxtaglomerular cells. Schricker, Karin, and Armin Kurtz. Institut f[umlaut]ur Physiologie I, Universit[umlaut]at Regensburg, D-93040 Regensburg, Germany
APStracts 2:0028F, 1995.
In this study we examine the role of membrane-permeable ions in renin secretion from renal juxtaglomerular cells. To this end extracellular Cl- (100 mmol/l) in the culture medium of isolated mouse renal juxtaglomerular cells was replaced by the permeable anion NO3- or by the membrane-impermeable anion isethionate. Alternatively extracellular Na+ (100 mmol/l) was substituted by the membrane -impermeable cation choline. The effects of these ion substitutions on basal and stimulated renin secretion were then examined. Renin secretion was stimulated by the adenylate cyclase activator forskolin (10 [mu]M), the NO-donor Na-nitroprusside (100 [mu]M), the calmodulin antagonist calmidazolium (10 [mu]M), by lowering extra cellular [Ca++] with EGTA (2mM) and by increasing extracellular [Ca++] from the normal value of 0.5 to 3 mM. Substitution of extracellular Cl- by isethionate, but not by NO3- inhibited basal renin release over 20 h of incubation. NO3- also did not change renin secretion stimulated by forskolin, nitroprusside, calmidazolium, EGTA or by increased extracellular Ca++. Isethionate, on the other hand, markedly attenuated the effects of EGTA and of increased extracellular Ca++, but not the stimulatory effect of forskolin, calmidazolium or nitroprusside. Substitution of Na+ by choline also attenuated basal renin secretion and renin secretion stimulated by lowering or raising extracellular Ca++. These findings suggest that, with respect to the dependency on permeable ions, at least two different pathways of regulated renin secretion from juxtaglomerular cells exist: A cation and anion dependent Ca++-related pathway and a less ionsensitive pathway for renin secretion activated by cyclic AMP and NO. 

Received 26 July 1994; accepted in final form 27 February 1995.
APS Manuscript Number F261-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.