Induction of Angiotensinogen Synthesis and Secretion by Angiotensin II

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Abstract
The effect of angiotensin II (ANG II) on the secretion of angiotensinogen was studied in isolated rat hepatocytes, obtained by the collagenase perfusion technique and Percoll-density gradient cen-trifugation, and in the isolated perfused rat liver. In isolated hepatocytes, steady state concentrations of about 1, 10 or 100 nM of ANG II during 90 min of preincubation resulted in a 5, 27 and 33% increase of angiotensinogen secreted during a subsequent 3 hour incubation period. Secretion rates during the last hour of incubation were increased by about 70% by the two higher ANG II concentrations, as compared to controls. Hydrocortisone also induced an increased secretion of angiotensinogen in hepatocytes. The effect of ANG II was prevented by saralasin, a competitive ANG II-antagonist and by actinomycin D. ANG II had no effect of the rate of albumin secretion and of total protein secretion. In the isolated perfused liver, ANG II induced a similar increase of angiotensinogen secretion, without affecting albumin and total protein secretion rates. These observations are consistent with the view that ANG II is participating in a feed back stimulation system of angiotensinogen synthesis and secretion in vivo.