MECHANISMS OF ANTIDIURESIS IN THE DOG AND IN THE RAT

Abstract

Rats in NaCl diuresis excrete 10 to 16 y/kg./hr. of antidiuretic hormone. In the urine of rats which received other dehydrating substances no antidiuretic hormone was found. Dogs with innervated or denervated kidneys during water diuresis excrete 9 to 28 7/kg./hr. of the hormone under morphine which is antidiuretically active. In spite of the fact that neither the antidiuretic hormone nor acetylcholine counteract diuresis produced by diuretics, morphine is antidiuretic also in this instance. This points to a humoral mechanism other than that originating in the posterior lobe of the hypophysis. Water diuresis in rats with innervated kidneys is counteracted by central anesthetics. Only small amts. of the antidiuretic hormone were found in the urine antidiuresis. Diuretic diuresis produced in such rats is not antagonized by pitressin or phenobarbital but is counteracted by morphine. Rats with decapsulated and denervated kidneys respond to water, urea, melamine, adenine, formoguanamine or caffeine with diuresis. Pitressin or phenobarbital are antidiuretically active during water diuresis, but the main antidiuretic effect of morphine is eliminated by the operation, and no antidiuretic effect at all remains during diuretic diuresis. Three different mechanisms of antidiuresis are apparent in these expts.: 1, the acetylcholine-antidiuretic hormone mechanism; 2, nervous control of the kidney of the rat; 3, a humoral factor in the dog different from the antidiuretic hormone.