Effects of pituitrin and cold on water exchanges of frogs.

HONG, SUK KI. (U. Rochester School Med. and Dentistry, Rochester, N. Y.) Effects of P’t ‘t z uz rin and cold on water exchanges of frogs. Am. J. PhysiO1. I 88(3): 439-442. rg57.-Net water transfer across the skin and urine formation by the kidneys were studied in frogs (R. @iens) especially under the influence of Pituitrin. The water uptake across the skin increased approximately 2.5-fold after the injection of Pituitrin, without any accompanying increase in urine formation. This Pituitrin effect in intact frogs was abolished totally or partly in extreme cold (1°C) or when the frogs were treated with nitrogen or KCN or IAA. These results are interpreted as evidence that the increase of net water transfer across the frog’s skin after the application of Pituitrin might be an active process, and it may be further postulated that the energy requirement for this increased transfer is small. RUNN B (I) found that the injection of the posterior pituitary hormone upset the frog’s water balance, even when it did not suppress urine output. Many workers have since confirmed the original finding and contributed to the understanding of the nature of this upset. The skin is of vital importance in the enhanced water uptake (2), and in fact the same result was observed in an isolated frog skin preparation (3). Recently, Sawyer (4) reported that the oxytocic substance is mainly responsible for this enhancing influence upon the skin after the injection of the posterior pituitary hormone, although the pressor substance also showed some influence. Currently, there are two contradictory theories to explain the possible mechanism of the Pituitrin effect: a) Koefoed-Johnsen and Ussing (5) postulate that active transport is not the main reason for the higher water transfer after the application of hormone, but Received for publication October 26, 1956. l The author is grateful to Dr. E. F. Adolph for his valuable suggestions. This work was made possible by a research contract from the Medical Research and Development Board, Office of the Surgeon General of the U. S. Army. 2 On leave from Severance Union Medical College, Seoul, Korea. Present address: Dept. of Physiology, University of Buffalo School of Medicine, Buffalo, N. Y. that this response may consist in an opening up of pores or creation of new pores to allow a more ready flow of water without increasing the total area available to diffusion (pore theory) : and b) Capraro and Garampi (6) postulate that the action of the posterior pituitary hormone is mainly an electro-osmotic effect, due to an increase in the potential difference between the two sides of the skin membrane and perhaps to an increase in the potential difference between the pore walls and the mobile solution which they contain, that is, active transport is involved (active transport theory). The present investigation attempts to decide between these two mechanisms of Pituitrin action upon frog’s water intake. The understanding of this skin mechanism might also enable us to visualize the action of the same hormone in the mammalian renal tubules.