Effect of Posterior Pituitary Extract on Permeability of Frog Skin to Water

Abstract

Rana pipiens kept in water responds to admn. of posterior pituitary extract by an increased rate of water intake through the skin. The effect of varying the concn. of NaCl in the external medium was studied and it was found that the frog could not imbibe water in response to pituitrin from solns. more concd. than 325 [image]Os/l. NaCl, which is approx. the osmolar concn. of body fluids. Expts. on isolated frog skin bathed in Ringer''s on the inside and water on the outside showed that pituitrin could cause a reversible increase in permeability of isolated skin to water. It appears that the primary site of action of pituitrin is on the skin of the frog, increasing its permeability to water and thus allowing an increased rate of inflow from a hypotonic external medium, and that this effect is independent of central nervous system control. Similarities as well as dissimilarities between this effect of pituitrin and the effect on the mammalian renal tubule are discussed.