THE EFFECTS OF VASOPRESSIN ON WATER UPTAKE OF THE TOAD, BUFO MARINUS, WHILE BATHED IN DIFFERENT HYPOTONIC SOLUTIONS

Abstract

SUMMARY The uptake of water with and without vasopressin was measured in the intact toad, Bufo marinus. When injected with vasopressin, toads sitting in tap water showed a significantly greater response than those sitting in distilled water. NaCl solutions of increasing concentrations potentiated the uptake of water in response to vasopressin over part of the hypotonic range. If the NaCl level was kept constant and glucose used to increase the concentration, there was a steady decrease in response as the concentration was increased towards isotonicity with the animal's body fluids. Uptake of water in response to vasopressin was far greater in sodium chloride than in either lithium or potassium chloride of the same concentration. The control water uptake was similar in the three solutions. Large doses of vasopressin brought about an increase in sodium loss through the toad's skin. The theoretical implications of these results are discussed in relation to possible mechanisms involved in this uptake of water.