Effects of Pitressin on Water Interchange in Normal and Decapitated Frogs

Abstract

Recently it was shown 1 that the permeability of the frog's skin is very much increased by injections of pitressin. Heller 2 also reported that frogs, previously decapitated, showed a smaller increase in weight than normal frogs after pitressin injections. Since Adolph 3 and others have reported pronounced increases in water uptake after pithing, it was of interest to repeat some of Heller's experiments with special reference to the effects of pitressin on decapitated frogs at various intervals of time after the decapitation. All of Heller's experiments were performed from 4 to 64 hours after decapitation. Our experiments can be separated into 2 groups— those done immediately after decapitation and from 26 to 48 hours after decapitation.

A complete experiment consisted in placing 4 normal frogs (30-40 gm.) in a glass container with enough water to nearly submerge them. The temperature was kept slightly below room temperature by the occasional addition of ice cubes. After weighing each frog accurately to 0.1 gm., on a triple-beam balance in a previously weighed container, 2 were decapitated according to the technique of Heller, which consists of placing one blade of the open scissors in the frog's mouth and making a sharp cut across the head at the level of the ears. The loosened head was then held in place by 2 stitches, which assisted in preventing severe hemorrhage. Pitressin (Parke-Davis) was then injected into the dorsal lymph sac of a normal and decapitated frog (0.1 cc. per 10 gm. body weight). The remaining 2, one a normal and another decapitated frog were kept as controls in the same container. Weighings were made at half hour intervals for a period of 6 hours.