EFFECT OF PHARMACOLOGIC DOSES OF VASOPRESSIN ON SODIUM-REABSORPTION IN RAT-KIDNEY

  • 1 January 1977
    • journal article
    • research article
    • Vol. 89  (5) , 987-991
Abstract
Administration of pharmacologic doses of vasopressin (50 mU[milliunits]/min per kg) to the rat significantly increase both urinary excretion of Na (0.20 .+-. 0.02 to 6.24 .+-. 0.76 .mu.eq/min) and urine flow rate (4.5 .+-. 0.5 to 30.5 .+-. 6.0 .mu.l/min). Simultaneous free-flow micropuncture studies demonstrated a decrease in end-proximal TF/P [tubular fluid-to-plasma] inulin ratios from 2.82 .+-. 0.15 to 1.90 .+-. 0.90 (P < 0.01), indicating decreased water reabsorption in this portion of the nephron. To reduce the influence of the pressor effect of these doses of vasopressin on the kidney, the aorta was constricted proximal to the renal arteries, this decreased urinary Na excretion to 2.87 .+-. 0.57 .mu.eq/min and urine flow rates to 16.6 .+-. 3.6 .mu.l/min compared with animals given vasopressin alone. End-proximal TF/Pinulin ratio was 2.01 .+-. 0.15, a value not significantly different than that in animals given vasopressin alone, suggesting a continued proximal inhibitory effect of vasopressin. Pharmacologic doses of vasopressin inhibit Na reabsorption in the proximal convoluted tubule and in distal portions of the nephron. The magnitude of Na excretion observed is a function both of vasopressin inhibition of Na reabsorption and the pressor effect of vasopressin.

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