DETERMINATION OF ANTIDIURETIC ACTIVITY IN THE RAT FOR STRUCTURAL ANALOGUES OF THE NEUROHYPOPHYSIAL HORMONES

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Abstract
A procedure for measuring the antidiuretic activity of the neurohypophysial hormones and their synthetic structural analogues in the hydrated rat in the dose range of 5-100 antidiuretic microunits is described. The technique of measurement allows the determination of diuresis over one-minute intervals, as well as the total amount of urine excreted over longer periods. The precision of the measurement is greatly increased by the use of a drop divider. The electrical conductivity of the urine is continuously recorded, and the conductivity and creatinine clearance are correlated with the urine flow. These techniques allow the precise determination of parameters such as the half-life of the antidiuretic effect, formal elemination constants, etc.; they can therefore serve for the comparison even of analogues showing qualitative differences in their antidiuretic effects from the chosen standard (arginine or lysine vasopressin), e.g. analogues of the hormonogen type with prolonged effects.