Effect of steroid depletion on the response of toad bladder to vasopressin.

1. We have investigated the water transport and short-circuit current (s.c.c.) response to vasopressin (1 mu./ml. and 100 mu./ml.) in isolated toad urinary bladders (Bufo marinus) following overnight incubation in the presence or absence of steroid-containing Ringer solution. 2. The water transport response to the lower dose of vasopressin (1 mu./ml.) was considerably reduced in 'steroid depleted' conditions, wheras the response to the higher dose of vasopressin (100 mu./ml.) was not similarly affected. 3. Aldosterone 3. Aldosterone 3. Aldosterone (10(-7)M) potentiated the water transport response to the lower dose of vasopressin (1 mu./ml.) but had no effect on the response to the higher dose (100 mu./ml.). 4. There was no effect of 'steroid depletion' or aldosterone treatment on the vasopressin s.c.c. response when measured as a percentage increase above basal levels. 5. In 'steroid depleted' conditions vasopressin (1 mu./ml.) maximally stimulated Na+ transport (s.c.c.) but a higher dose of vasopressin (100 mu./ml.) was required for maximum water transport. 6. We have failed to obtain any potentiation effect of corticosterone (10(-7)M) on the water transport or s.c.c. response to vasopressin (1 mu./ml.).