Effect of chronic ouabain infusion on food, water, and nacl intake, body composition, and plasma hormones of sprague-dawley rats

Abstract

To examine whether the sodium-potassium pump (Na +,K +-ATPase) mediates food or NaCl intake, male Sprague-Dawley rats with ad lib access to food, water, and 300 m M NaCl solution were infused for 27 days with the Na +,K +-ATPase inhibitor, ouabain (4, 8, 16, 32, or 64 μg/h, SC). Ouabain significantly decreased NaCl preference and increased body weight but had no effect on food or NaCl intake, carcass fat, protein, or ash content. Ouabain's effect on NaCl preference was apparently due to a nonsignificant increase in water intake, and its effect on body weight was due to a significant increase in carcass water content. During the first 5 days of treatment, 4–32 μg/h ouabain decreased and 64 μg/h ouabain increased plasma corticosterone levels relative to controls. At the end of the experiment, all the ouabain-treated rats had significantly elevated plasma ouabain levels but normal plasma osmolarity, solids, pH, sodium, calcium, glucose, insulin, aldosterone, and corticosterone levels. The groups receiving 4–32 μg/h ouabain also had normal plasma concentrations of potassium, ACTH, and renin activity. The group receiving 64 μg/h ouabain had elevated ACTH and potassium levels and reduced plasma renin activity. These results suggest that chronic administration of low doses of ouabain specifically increases water retention. The hypotheses that the sodium-potassium pump mediates food and NaCl intake are neither supported nor refuted.