Tracer microinjection studies of effect of ADH on renal tubular diffusion of water

¹ Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina

The tracer microinjection technique was utilized to study the effect of vasopressin (ADH) on transtubular water diffusion in rats with diabetes insipidus. Inulin-C¹⁴ and tritiated water (HTO) were simultaneously injected into the same distal convolutions before and after intravenous administration of ADH, and their recovery in the urine of the injected kidney measured. Urine flow was maintained constant by intravenous infusion of mannitol. ADH had no effect on inulin recovery, but delayed and reduced HTO excretion. Total HTO recovery averaged 19% before and 11% after ADH, and direct HTO recovery averaged 8% before and 1% afterward. A theoretical treatment of the data is presented which leads to the conclusion that ADH increases the permeability to water diffusion of the luminal surface of the cellular membranes of the distal convolutions and/or collecting ducts, but has no effect on permeability to water diffusion of their basal surfaces.

Key Words: kidney micropuncture • tracer microinjection technic • vasopressin • antidiuretic hormone • renal tubule • water permeability

Submitted on December 8, 1964