Relationship between renin mRNA and renin secretion in adrenalectomized, salt-depleted, or converting enzyme inhibitor-treated rats.

Renin secretion was stimulated in rats by adrenalectomy (ADX), by treatment with the converting enzyme inhibitor enalapril (MK 421), or by feeding a low salt diet plus furosemide treatment (FUR). Relative amounts of renin mRNA were measured by densitometric Northern blot analysis using a 32P-labeled 700 bp mouse submaxillary gland cDNA fragment as hybridization probe. Renin secretion was measured in isolated kidneys taken from pretreated rats. Treatment resulted in a 4.4-, 7- and 12.7-fold increase in total renin mRNA in kidneys of ADX, MK 421 and FUR rats, respectively. Plasma renin levels increased 5-, 9- and 12-fold in ADX, MK 421 and FUR rats, whereas ex vivo secretion rates from the isolated kidney were 4.7-, 0.5- and 4.2-fold, respectively, that of controls. Thus, a close relationship between increases in renin secretion in vivo (reflected by plasma renin concentration) and renin mRNA exists, whereas secretion rates in the isolated perfused kidney ex vivo change in a non-proportional fashion.