Guanylylimidodiphosphate enhances the vasopressin- and vasotocin-induced osmotic water flow with no effect on the sodium transport of the frog bladder.

The effects of guanylylimidodiphosphate [Gpp (NH) p] on the vasopressin- and vasotocin-induced osmotic water flow and sodium transport across the bladder of the frog, Rana catesbiana, were examined. Gpp (NH) p enhanced both the vasopressin- and vasotocin-induced water flow, while it did not affect that of the sodium transport. These results suggest that the neurohypophysial hormone-induced water flow is regulated by the guanine nucleotide regulatory site of the adenylate cyclase, while the sodium transport is not regulated at the regulatory site.