Angiotensin II receptors and aldosterone production in rat adrenal glomerulosa cells.
Specific receptors for angiotensin II (A II) were demonstrated in membrane fractions and collagenase-dispersed cells from the zona glomerulosa of the rat adrenal gland. The equilibrium association constant (Ka) of the A II binding sites was similar in particulate fractions (2.0 +/- 0.4 (SE) X 10(9) M-1) and intact glomerulosa cells (1.8 +/- 0.3 X 10(9) M-1). Specific binding of [125I]iodo-A II was enhanced by increasing sodium concentration, and in the presence of dithiothreitol, EDTA, and EGTA. Plasma membrane fractions prepared by density gradient centrifugation showed increased binding of [125I]iodo-A II, and were correspondingly enriched in adenylate cyclase and sodium-potassium-dependent ATPase. Steroid production by collagenase-dispersed adrenal glomerulosa cells was highly responsive to A II and ACTH. Significant increases in aldosterone and corticosterone production were elicited by A II concentrations as low as 3 X 10(-11) M, equivalent to normal blood levels of A II in rats (5 X 10(-11) M). The maximum increase in aldosterone production, of 6--7 times the basal value, was obtained at 10(-9) M A II. Dispersed capsular cells were also highly sensitive to ACTH, responding to concentrations down to 3 X 10(-12) M with increased aldosterone production, reaching a maximum aldosterone response of 20-fold above the basal value. The magnitudes of the aldosterone and corticosterone responses to A II in capsular and fasciculata-reticularis cells were commensurate with the distribution of A II receptors, which were 11-fold more concentrated in capsular cells. The ability of A II to evoke aldosterone production at physiological concentrations, and the correspondence between A II binding and steroidogenesis in capsular cells, demonstrate the functional importance of A II receptor sites in the zona glomerulosa of the rat adrenal cortex.
D000311:Adrenal Glands / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000450:Aldosterone / Q000096:biosynthesis*; D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002414:Cations, Monovalent; D007700:Kinetics; D008297:Male; D051381:Rats; D011945:Receptors, Angiotensin / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
D002414:Cations, Monovalent; D011945:Receptors, Angiotensin; D011956:Receptors, Cell Surface; D000804:Angiotensin II; D000450:Aldosterone; D000324:Adrenocorticotropic Hormone