| Abstract: | Bovine adrenal cells were isolated from the subcapsular region of the gland to obtain cultures enriched in cells of the zona glomerulosa. The cells kept in primary cultures were shown to respond to angiotensin II and adrenocorticorticotropin (ACTH) by a significant increase in aldosterone production. These primary adrenal cultures were used to study the effect of angiotensin II on LDL metabolism. Addition of angiotensin II for 48 h to the culture medium resulted in a 200-300% increase in LDL metabolism, and the lowest effective concentration was 10(-8) -10(-9) M. The angiotensin II effect became evident after 12-16 h of incubation. To compare the metabolism of the 125I-labeled protein moiety to that of cholesteryl ester of LDL, the lipoprotein was labeled also with cholesteryl linoleyl ether, a nonhydrolyzable analog of cholesteryl ester. Under basal conditions and in the presence of angiotensin II or ACTH the ratio of 3H]cholesteryl linoleyl ether to 125I indicate some preferential uptake of the cholesteryl ester moiety. Stimulation of specific LDL binding at 4 degrees C and LDL metabolism at 37 degrees C by 10(-7) M angiotensin II occurred at all concentrations of LDL studied. Linearization of the kinetic data showed that angiotensin II increased the LDL receptor number significantly but not the affinity of the LDL receptor for its ligand. The present findings indicate that in analogy to ACTH, angiotensin II can influence receptor-mediated uptake of LDL by adrenal cortical cells. It remains to be shown whether the angiotensin II effect on LDL metabolism is limited to adrenal cells or will affect other cells which express the angiotensin II receptor. |
