Immunochemical studies on biosynthesis of rat plasma angiotensinogen and its regulation by cortisol

Glucocorticosteroid hormones increase the level of rat plasma angiotensinogen by increasing its rate of synthesis. Two forms of plasma angiotensinogen have been purified differing with respect to molecular weight and affinity to concanavalin A. Immunochemical studies using antibodies raised against the separated forms of angiotensinogen revealed cross-reactivity with both antigens. Both antibodies were able to quantitatively precipitate the angiotensinogen activity present in rat serum samples. Cortisol increased the total amount of plasma renin substrate without changing the relative amounts of both angiotensinogen forms. mRNA coding for plasma angiotensinogen was determined by in vitro translation of poly(A)-containing RNA and immunochemical analysis of translation products. Angiotensinogen mRNA could be detected in total poly(A)-containing RNA isolated from rat liver, but not in mRNA isolated from brain, although angiotensinogen has been reported to be present in the latter organ. The level of hepatic mRNA coding for plasma angiotensinogen was high in rats treated with cortisol, but not detectable in animals depleted from endogenous glucocorticosteroids by bilateral adrenalectomy.