Isotonic NaCl Diuresis in Rats

Antidiuresis and Chloruresis Produced by Posterior Pituitary Extracts

¹ From the Department of Physiology, Harvard Medical School, Boston, Massachusetts

Prolonged, steady state, isotonic saline diuresis was produced by intravenous infusion in single, unanesthetized rats. The actions of single, intravenous doses of vasopressin, oxytocin and posterior pituitary solution were studied, with particular emphasis on concurrent changes of NaCl and water excretion. During isotonic saline diuresis vasopressin was antidiuretic, and in larger doses, chloruretic. Oxytocin was diuretic and chloruretic. Posterior pituitary solution was phasically diuretic and strongly chloruretic. Suitable doses of each were also injected during infusions of 0.6, 0.3, 0.23, 0.15, 0.077, 0.030 and 0.00 m NaCl, sufficient dextrose being added in the last three to make the infusate isotonic with blood. The effects of these infusates on the antidiuretic and chloruretic action of vasopressin, oxytocin and posterior pituitary solution are described. In general, decreasing the NaCl content of the infusion enhanced antidiuretic action and tended to conceal chloruretic action. Conversely, increasing the NaCl content of the infusion, within physiological limits, enhanced chloruresis, diminished antidiuretic action and enhanced diuretic action. Chloruresis blocked or even reversed an expected antidiuresis. The bearing of these findings on methods of assaying materials for their effects on NaCl and water excretion is discussed briefly.