THE EFFECTS OF INFUSIONS OF CHLOROTHIAZIDE ON URINARY DILUTION AND CONCENTRATION IN THE DOG

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Abstract
The intravenous infusion of chlorothia-zide in dogs undergoing maximal water diuresis resulted in an immediate rise in solute clearance (CoSm) and fall in free water clearance (CH2O) without related changes in volume. The decreased CH2O was quantitatively related to the increased Cosm. During hydropenia and solute diuresis this agent increased TcH2O volume of solute free water reabsorbed at high rates of solute excretion that were associated with a diminishing TCH2O in the absence of chlorothiazide. At lower rates of solute excretion the drug did not alter TcH2O. It is suggested that TCH2O diminishes at high rates of solute excretion due to the failure of complete osmotic equilibration of the dilute fluid traversing the distal convolution. It is therefore concluded that chlorothiazide interferes with the renal tubular transport of solute (sodium) in the diluting portions of the distal convolution.