Effect of aldosterone on vascular angiotensin II receptors in the rat.
The effect of aldosterone on the density and affinity of binding sites for 125I-labelled angiotensin II was investigated in a particulate fraction prepared from the rat mesenteric arteriolar arcades. The infusion of aldosterone 6.6 micrograms/h intraperitoneally via Alzet osmotic minipumps for 6 d produced an increase in the density of binding sites for 125I-labelled angiotensin II without change in affinity. After sodium depletion, mesenteric artery angiotensin II receptors were down-regulated as expected. An increase in the number of binding sites could be found when aldosterone was infused into sodium-depleted rats with no change in the elevated plasma renin activity. The intraperitoneal infusion of angiotensin II (200 ng X kg-1 X min-1 for 6 d) simultaneously with aldosterone resulted in down-regulation of vascular angiotensin II receptors, whereas after intravenous angiotensin II infusion (at 60 ng X kg-1 X min-1) the density of angiotensin II binding sites rose with aldosterone infusion. Plasma renin activity (PRA) was reduced and plasma angiotensin II increased in a dose-dependent fashion after angiotensin II infusion. An aldosterone concentration of 3 ng/mL for 18 h produced an increase in the number of angiotensin II binding sites in rat mesenteric artery smooth muscle cells in culture. We conclude that increased plasma aldosterone may result in up-regulation of vascular angiotensin II receptors independently of changes in plasma renin activity, and may in certain physiological states effectively antagonize the down-regulating action of angiotensin II.
D000450:Aldosterone / Q000494:pharmacology*; D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000187:drug effects; D008638:Mesenteric Arteries / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011188:Potassium / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000187:drug effects*; D011956:Receptors, Cell Surface / Q000187:drug effects*; D012964:Sodium / Q000652:urine
D011945:Receptors, Angiotensin; D011956:Receptors, Cell Surface; D000804:Angiotensin II; D000450:Aldosterone; D012964:Sodium; D011188:Potassium