Differentiation of an (amphibian) water balance principle from the antidiuretic principle of the posterior pituitary gland
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AN injection of mammalian posterior pituitary extract into an amphibian kept in water causes a gain of weight due to a temporary increase of the animal's body water. The smallest dose which produces a significant increase of weight in frogs (Rana esculenta) is approximately 0x1 unit or 100 milliunits (mU.) of a posterior pituitary preparation [Heller, 1930a]. (Boyd & Brown [1938], working with American frogs (Rana pipiens), obtained a comparable figure.) It has recently been shown [Heller, 1941 a] that the pituitary gland ofthe frog contains an antidiuretic activity equivalent to only about 3*5 mU. pitressin. In Niew of the discrepancy between the small amount of antidiuretic principle found in the frog pituitary gland and the minimum amount of a (mammalian) posterior pituitary extract needed to produce an increase of body water it looks as though the antidiuretic hormone had little significance for the regulation of the water balance of amphibians. Extracts of frog pituitary glands were therefore prepared and their action on the water metabolism of frogs tested.