CROSS-CIRCULATION EXPERIMENTS ON UNANESTHETIZED RATS .I. TECHNIQUE AND SOME RESULTS CONCERNING HUMORAL TRANSMISSION OF DIURETIC AND ANTIDIURETIC STATES

1. A method is presented which allows cross-circulation experiments with relatively high flow rates (e.g. 25% of blood volume/min) to be performed on conscious rats. The effectiveness of blood- and body-water-exchange is determined with dilution methods and the dynamics of these processes analysed. 2. The influence of differences in the state of hydration of the parabionts on their respective diureses is examined. Changes of diuresis due to hormone exchange are seen far earlier than can be accounted for by exchange of body-water and minerals (convergence of two states of hydration). This leads to the practicability of a very sensitive hormone assay (e.g. ADH test). 3. The blood of a normally hydrated rat shows large differences in antidiuretic activity over relatively short periods of time. 4. The method can be employed for the determination of the amounts of hormone liberated (e.g. in acute hemorrhage). © 1969 Springer-Verlag.