Increased water permeability of the bullfrog (Rana catesbiana) bladder in vitro in response to synthetic oxytocin and arginine vasotocin and to neurohypophysial extracts from nomammalian vertebrates.

Abstract

Ncurohypophysial hormones accelerate the passage of water across the wall of the isolated bullfrog (Rana catesbiana) bladder in vitro. Net water movement may be in either direction depending on the existing osmotic gradient. Net sodium transport from mucosal to serosal surface has little influence on the magnitude or direction of water movement. The increased net water movement is considered, therefore, to be clue to a change in water permeability, probably resulting from the dilatation of pores. Oxytocin is more active than vasopressin in enhancing water permeability. The synthetic analogue arginine vasotocin is many times more active than oxytocin. The ratio of frog-bladder activityto oxytocic activity is high in ncurohypophysial extracts from a lamprey, a teleost, a frog, a toad, a marine turtle, and the chicken. This suggests that arginine vasotocin may be a natural hormone in the neurohypophyses of many non-mammalian vertebrates.