AJP - Endocrinology and Metabolism, Vol 270, Issue 3 E386-E392, Copyright © 1996 by American Physiological Society
Chronic ouabain infusion does not cause hypertension in sheep
G. B. Pidgeon, A. M. Richards, M. G. Nicholls, C. J. Charles, M. T. Rademaker, K. L. Lynn, R. R. Bailey, L. K. Lewis and T. G. Yandle
Department of Nephrology, Christchurch Hospital, New Zealand.
Ouabain is claimed to be a hormone of adrenal origin, capable of raising
arterial pressure in rats. We infused ouabain in conscious sheep under
carefully controlled circumstances to determine its effects on blood
pressure, urine electrolytes, and vasoactive hormones. Eight healthy ewes
were studied while taking a constant intake of dietary sodium and
potassium. Ouabain infusion at 0.25 mg daily over 22 days reduced heart
rate and arterial pressure and had no effect on pressor responsiveness to
incremental intravenous infusions of angiotensin II. Ouabain induced minor,
but statistically significant, decrements in urine volume, urinary sodium
excretion, plasma renin and angiotensin II concentrations, and a rise in
plasma aldosterone and cortisol. Plasma ouabain levels averaged 1.37 +/-
0.28 nmol/l during ouabain infusion. In conclusion, high-dose chronic
ouabain infusion in sheep did not elevate arterial pressure or alter
pressor responsiveness to angiotensin II, was antidiuretic and
antinatriuretic, and induced minor perturbations in circulating renin,
angiotensin II, aldosterone, and cortisol.
