Abstract
1. Medullectomized rats showed a diminished diuretic response to ingested water.
2. Subcutaneous injection of adrenaline in a small dose, which failed to increase urine output in normal rats, caused an increase in the water excretion rate of medullectomized rats. Treatments with adrenaline, 2 hours prior to water load or successively for 3 to 4 weeks, restored the lowered diuretic response of medul lectomized rats to normal level.
3. Pitressin was more effective to elicit antidiuresis in medullectomized rats than in normal ones.
4. Vasopressin inactivating capacity of liver tissue was reduced after medullec tomy. The reduced inactivation restored to normal level after treatments with adrenaline. In vitro addition of adrenaline into incubation medium of liver homogenate did not affect the inactivating system.
5. Serum from medullectomized rats contained more antidiuretic activity than that from normal rats. The accumulation of antidiuretic material in serum in the absence of adrenal medulla could be prevented by chronic treatments with adrenaline.
