Vasotocin-like activity in the plasms of the euryhaline frog (Rana cancrivora) after transfer from fresh water to saline.

When Rana cancrivora were collected from fresh water and dehydrated (weight loss 4-10%) by exposure to saline, the plasma titre of hydro-osmotic activity, measured by amphibian bladder assay, was increased three-to fourfold. This activity, which was abolished by thioglycollate and by incubation with tyrosinase or trypsin, was ascribed to vasotocin. The plasma vasotocin activities (hydrated and dehydrated frogs respectively) were estimated to be 0-03-0-5 and 0-15-0-25 mug/1; if referred to oxytocin as a standard the equivalent values were 10 and 30-60 mu./ml. Assuming that the increase represented released pituitary hormone, the amount of vasotocin released by osmotic dehydration was calculated to be of the order of 1 ng. Pituitary glands of hydrated and dehydrated frogs were estimated to have 0.15 and 0-18 mug vasotocin/gland respectively. The possible physiological function of released vasotocin in promoting reabsorption of urea from the urinary bladder is discussed in relation to the euryhaline ability of R. cancrivora.