RENIN RELEASE FROM PERMEABILIZED JUXTAGLOMERULAR CELLS IS STIMULATED BY CHLORIDE BUT NOT BY LOW-CALCIUM

The intracellular concentrations of calcium and chloride have been sug gested to be involved in the control of renin secretion from juxtaglom erular (JG) cells. We have tested these propositions on permeabilized JG cells. Rat glomeruli with attached JG cells were isolated by the ma gnetic iron technique, superfused, and permeabilized by 20 mu M digito nin for 12 min. The calcium concentration was varied with Ca ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) b uffers [0 (5 mM EGTA without calcium), 17, 73, 170, 440, or 700 nM and 1.5, 15 or 150 mu M]. These maneuvers had no effect on renin release, while 1.5 mM calcium caused a stimulation, which was not inhibited by 50 mM sucrose. Isosmotic increases in the chloride concentration to 2 5, 60, and 132 mM resulted in prompt stimulations of renin release. Si milarly, iodide and nitrate stimulated renin release. We conclude that renin release from permeabilized JG cells is unaffected by calcium co ncentrations in the nano- and micromolar range, while the release is s timulated by chloride or other permeant anions. We suggest that in int act JG cells an increase in calcium inhibits renin release through act ivation of chloride channels followed by a drop in the intracellular c hloride concentration. The stimulation caused by the high calcium conc entration may be a toxic effect or may be due to stimulation of the fu sion between granules and cell membrane in a way analogous to other se cretory cells.