Abstract
1. The proposition that changes in renal calcium excretion during vasopressin administration are positively correlated with concurrent changes in urine hydrogen ion concentration was tested by administration of vasopressin into twelve conscious diuresing sheep receiving either alkalinizing or acidifying infusions. 2. Vasopressin-induced antidiuresis in sheep with alkaline urine was associated with significant increases in urinary pH and decreases in the rate of calcium excretion whereas antidiuresis in sheep with acid urine was associated with significant decreases in urinary pH and no consistent effect on calcium excretion. 3. Magnesium excretion increased during vasopressin administration in most experiments regardless of urinary pH changes. 4. Vasopressin administration did not significantly alter the rate of excretion of sodium, potassium, chloride and phosphate or the rates of sodium, potassium, chloride, inulin, para-aminohippurate and osmolal clearance in sheep with either acid or alkaline urine. Potassium excretion and clearance in sheep with alkaline ruine was higher than that of sheep with acid urine during vasopressin infusion. 5. The results support the hypothesis that changes in renal tubular hydrogen ion concentration or bicarbonate concentration caused by water reabsorption from the collecting duct and possibly the late distal tubule could be part of the explanation for changes in renal calcium excretion which occur during vasopressin-induced antidiuresis.