Hormonal and pharmacological alteration of angiotensinogen secretion from rat hepatocytes

Isolated hepatocytes were prepared from rat liver by collagenase perfusion and density gradient centrifugation. The hepatocyte preparation released angiotensinogen at a basal rate of 50-120 pmol/g wet weight per h. Release was linear with time for at least 4 h. Angiotensinogen secretion was reduced in the presence of actinomycin D, and inhibited by cycloheximide, puromycin, colchicine and vinblastine. In the presence of tunicamycin, an inhibitor of N-glycosylation, the secretion of angiotensinogen as well as total protein and albumin secretion were diminished. Hepatocytes from nephrectomized rats exhibit an increased secretion rate of angiotensinogen, whereas total protein secretion was unaltered. Preincubation of hepatocytes with hydrocortisone (0.1 mM) or angiotensin II (10 nM) induced an increase of angiotensinogen release. There was no concomitant increase of total protein or albumin secretion, indicating that these effects are not the expression of a general stimulation of protein synthesis and secretion.