Effect of angiotensin II infusion in rats on Na,K-ATPase activity in renal cortical microsomal preparations.
Direct dose-dependent effects of angiotensin II on renal tubular sodium reabsorption have been demonstrated. Alterations in tubular sodium reabsorption may occur via modulation of renal Na,K-ATPase activity. Thus, these experiments were undertaken to ascertain whether angiotensin II could influence renal cortical Na,K-ATPase activity. Angiotensin II, 495 ng/microliters/h, or vehicle (controls) was infused for 24 h via miniosmotic pumps 48 h after rats were adrenalectomized and implanted with osmotic pumps containing 12.5 micrograms/microliters corticosterone (Treatment I) or both corticosterone and 0.2 microgram/microliter aldosterone (Treatment II), and in rats receiving 3% NaCl in their food (sodium loaded, Treatment III). Rats receiving Treatments I and III received saline to drink. Renal cortical microsomal membranes were prepared, and the effects of angiotensin II infusion on the K1/2 and Vmax for Na, K, and ATP determined. Angiotensin II infusions were associated with (i) a decrease (P less than 0.001) in the K1/2 for Na activation of Na,K-ATPase from 14 +/- 3 to 6 +/- 1 (n = 4 experiments), 16 +/- 1 to 12 +/- 1 (n = 5), and 12 +/- 3 to 7 +/- 1 (n = 5) mM (means +/- SE) for treatments I, II, and III, respectively; (ii) no changes in the K1/2 for K activation or the Km for ATP; (iii) no changes in the Vmax for Na, K, or ATP; and (iv) no change in Mg-ATPase activity. We conclude that angiotensin II infusion is associated with a decrease in the K1/2 of renal cortical Na,K-ATPase activity for sodium. This action of angiotensin II on the enzyme activity may contribute to the regulation of tubular sodium transport.
Brown
G
G
School of Nursing, State University of New York, Buffalo 14214.
Douglas
J
J
D000315:Adrenalectomy; D000450:Aldosterone / Q000494:pharmacology; D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D003345:Corticosterone / Q000494:pharmacology; D007263:Infusions, Parenteral; D007672:Kidney Cortex / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology*; D011188:Potassium / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012083:Renin / Q000097:blood; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D000804:Angiotensin II; D000450:Aldosterone; D012964:Sodium; D012083:Renin; D017301:Ca(2+) Mg(2+)-ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D003345:Corticosterone