Increased sensitivity of ADH bio-assay in rats by change in diet.

1. Water-loaded rats anaesthetized with ethanol were used for the detection of antidiuretic hormone (ADH). 2. Litter-mates were divided into groups and placed on different diets during the fourth week of life directly after weaning, and maintained on their respective diets for approximately 1 month and their sensitivity to vasopressin was determined. 3. The rats maintained on a diet of only vegetable or vegetable plus casein supplement showed a greater sensitivity to exogenous vasopressin than rats maintained on a standard laboratory diet (pellets). 4. It is proposed that the quantitative relationship between ADH and urine flow is dependent upon the previous history of water consumption.