mersalyl 2 ml. intramuscularly, over a period of six days

Renal cortical slices (about 5 x 5 x 0.5 mm) from New Zealand white rabbits, fed a sodium-deficient rabbit Chow for 2 to 3 weeks, were prepared. Two or three slices were incubated at 37’C for two to three periods of 1 hr each, unless otherwise indicated, in 2 ml of medium that was continuously gassed with 100% 02. The composition of the standard incubation medium was (in mM): NaC1, 145; KC1, 5.5; CaCl2, 2.0; MgCl2, 1.0; glucose, 10; N-2-hydroxyethylenepiperazine-N-2-ethanesulfonic acid, 10. The pH was adjusted to 7.0. The Na+-free and Cl--free medium was prepared by substituting Na+ with K+, and Cl- with isethionate (2-hydroxyethanesulfonate), respectively. The Na+-free modified medium did not contain 2 mM CaCl2 but contained 2 mM EGTA. In this Na+-free, high K+ medium, Ca2+ was found to exert a marked inhibitory effect on renin secretion. Therefore, Ca2+ was excluded from the medium to avoid the complication of the inhibitory effect of Ca2+ on renin secretion superimposed on the stimulatory effect of EA. The first 1-hr incubation in the standard medium served as the control. For subsequent periods, slices were incubated in media containing different ionic compositions or with MERSALYL (10mkM-3mM). In parallel, slices were incubated in the standard medium without test reagents as the time control. At the end of each incubation period, medium was collected and renin activity was determined by radioimmunoassay of angiotensin I generated following incubation of an aliquot of collected medium with plasma of 48-hr nephrectomized rabbits.