The effects of bilateral adrenalectomy on renal function in the lizard Varanus gouldii (Gray)

Abstract

The effects of bilateral adrenalectomy and steroid replacement therapy on renal function of the lizard Varanus gouldii are reported during water loading and salt loading. Plasma potassium concentrations increase and glucose concentrations decrease following adrenalectomy; plasma sodium concentrations, however, are unchanged. Normal plasma electrolyte and glucose concentrations are maintained in adrenalectomised animals by the daily injection of 1 mg/kg dexamethasone phosphate and 20 μU/kg glucagon. In salt-loaded animals no change in the renal handling of electrolytes is observed subsequent to adrenalectomy, but the fractional reabsorption of both sodium and chloride ions is significantly reduced in water-loaded animals. Acute injection of exogenous aldosterone significantly increases the fractional reabsorption of sodium ions and enhances the tubular secretion of potassium ions in salt-loaded adrenalectomised animals, and also further increases the fractional reabsorption of sodium ions in water-loaded animals. The data indicate that aldosterone functions as a physiological mineralocorticoid in V. gouldii, acting to limit sodium excretion and promote potassium excretion.