Iso-renin secretion from rat brain cortex slices in vitro under the influence of ions and electrical stimulation.

The aim of this study was to obtain additional data concerning the influence of changes in osmolarity and ionic composition on iso-renin secretion from rat brain cortex slices. The slices were isolated and superfused in vitro according to the technique of Pull and McIlwain (1972). The secretion of iso-renin was strongly stimulated by an increase of Na+ concentration. Iso-renin output almost doubled upon raising NaCl from 120 to 240 mM. Decrease of the NaCl concentration to 60 mM resulted in a reduced iso renin secretion while addition of tetrodotoxin (TTX) (60 micron) did not significantly alter the iso-renin content of brain slices. Changes in osmotic pressure were without significant influence. Electrical stimulation or elevation of extracellular K+ concentrations enhanced iso-renin secretion. Furthermore, Ca2+ ions seem to increase both the content and the release of cerebral iso-renin.