STUDIES OF THE CARBON DIOXIDE AND OXYGEN TENSIONS OF URINE DURING APPLICATION OF THE STOP-FLOW TECHNIQUE

Abstract

Studies by the stop–flow technique were carried out in dogs in which diuresis had been induced with water, with and without the addition of bicarbonate. Urine samples from the collecting duct had greater maximal CO2 tension than was recorded simultaneously in arterial blood, and this peak occurred during infusion of carbonic anhydrase as well as during its inhibition by acetazolamide. With the former procedure, curves of CO2 tension were almost identical with those in standard control experiments. After administration of acetazolamide the values were greater, even when CO2 tension in arterial blood was > 60 mm Hg; otherwise, the curves were of similar shape. Lowest values for O2 tension in urine were recorded from the collecting duct region, and they persisted when urine flow was increased by the administration of acetazolamide or when the dog breathed 100% oxygen. The curves were of similar shape but values were slightly greater during oxygen breathing. The results obtained reflect the operation of hemodynamic mechanisms in the renal medulla, during application of the stop–flow technique.