Stimulation of vascular Na-K pump with subpressor angiotensin II in rats.
The effect of subpressor doses of angiotensin II (ANG II) on vascular Na-K pump activity and Na-H exchange, two transmembrane signals of trophic stimulation of vascular muscle, was investigated. Male Sprague-Dawley rats (350-400 g) were given subpressor doses of ANG II by osmotic minipump intraperitoneally for 24 hr or 7-10 days. Control rats received sham procedure/vehicle infusion. Na-K pump activity (86Rb uptake), total and intracellular (Li exchange at 4 degrees C) Na content, and amiloride-sensitive and -insensitive Na uptake of aortas were measured ex vivo. Ouabain-sensitive 86Rb uptake of aortas of rats receiving 80-100, 160-180, and 240-260 ng/kg.min-1 of ANG II for 24 hr was 26.6 +/- 3.5, 28.8 +/- 3.4, and 29.1 +/- 2.6 nmol/mg dry wt.15 min-1 (mean +/- SD, n = 7-12), respectively, compared with 25.2 +/- 3.8 in controls (n = 23, P less than 0.01). These increases were maintained at 7-10 days. After 24 hr and 7-10 days of ANG II treatment, the total Na content of aortas was increased by 9.2% (P less than 0.01) and 7.6% (P less than 0.02), respectively, without a change in intracellular Na content, indicating accumulation of excess extracellular Na. Total and amiloride-sensitive Na uptake of the aorta was unchanged after 24 hr or 7-10 days of ANG II administration. The dry weight of anatomically defined segments of the aorta was 40 +/- 3.8 mg/kg body wt (n = 25) after 24 hr and 42 +/- 4.4 (n = 20) after 7-10 days of ANG II administration, compared with 37 +/- 4.8 (n = 15, P less than 0.05) and 37 +/- 4.9 (n = 17, P less than 0.01) in appropriate controls. Increased Na-K pump activity may signal the onset of trophic stimulation of vascular muscle by ANG II.
Simon
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Department of Medicine, Veterans Administration Medical Center, Minneapolis, Minnesota 55417.
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects*
D000804:Angiotensin II; D012083:Renin; D000254:Sodium-Potassium-Exchanging ATPase