Regulation of Na+-K+ pump activity in erythrocytes and blood pressure in anephric rats

This study was designed to explore factors involved in the regulation of Na-K pumps in erythrocytes and blood pressure in anephric Sprague-Dawley female rats. Twenty-four hours following bilateral nephrectomy, the rats were given a 1-h infusion of 1 ml of either 0.9% or 5.4% saline, or 5% or 30% glucose. At the completion of the infusion, tail blood pressure was determined and blood was drawn for the measurement of the ouabain-furosemide-sensitive sodium efflux rate constant in erythrocytes. Infusion of 5.4% saline or 30% glucose caused a significant reduction in the erythrocyte sodium efflux rate constant, more pronounced with the former, and an elevation in blood pressure. Nephrectomy or infusion of 0.9% saline or 5% glucose had no effect on either parameter. These findings suggest that in anephric rats (1) extracellular fluid hyperosmolality rather than extracellular fluid volume expansion inhibits the Na-K pump in all cells; (2) a Na-K pump inhibitor is involved in the genesis of hypertension.