EN
The renal actions of oxytocin were studied in the conscious unrestrained rat infused with 0.077 M saline at a rate of 150 µl/min. During the control period volume and sodium excretion reached stable equilibria, the rates being equal to those infused. Administration of oxytocin at 200 pmol/min produced plasma oxytocin levels of 26.0±2.1 pmol/1 and caused a significant diuresis and natriuresis. Renal responses could also be seen with a lower dose of 30 pmol/min which produced plasma levels of 5.1 ±0.5 pmol/1 while a dose of 15 pmol/min which produced no significant increase in the plasma oxytocin had no renal effect. It appears that oxytocin has a natriuretic action in concentrations within the physiological range.