Glucocorticoid and thyroid hormone regulation of angiotensinogen gene expression in a pancreatic islet cell line

The renin-angiotensin system is an important regulator of blood pressure and volume homeostasis in mammals. Angiotensinogen, a precursor of the octapeptide angiotensin II and an effector of the renin-angiotensin system, is synthesized in numerous rat tissues. Angiotensinogen is expressed in an islet cell line (RIN 1056A) derived from a rat pancreatic tumor. Angiotensinogen mRNA detected by Northern analysis is abundant in the cell line and is approximately 200 bases longer than the mRNA isolated from rat liver, due to both a longer poly(A) tract and the use of a second polyadenylation site. Dexamethasone is a potent inducer of angiotensinogen mRNA, producing a progressive accumulation from 3 to 96 hr in culture (9-fold above control levels). The dexamethasone effect is competitively inhibited by the glucocorticoid antagonist RU486, and transcription rate assays using isolated nuclei indicate that the effect is primarily at the transcriptional level.