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A Mechanism for Adenosine 3',5'-Monophosphate Regulation of Vasopressin Secretion^*

Division of Pharmacology and Therapeutics, Faculty of Medicine, University of Calgary Calgary, Alberta, Canada T2N1N4

Address requests for reprints to: Dr. Ron Mathison, Département de Physiologie de l’Université, Ecole de Médecine, 1121 Geneve 4, Switzerland.

Abstract

The actions of cAMP and theophylline on potassium- stimulated vasopressin release from the isolated neural lobe of the rat were studied. Biphasic effects were observed. An inhibition of vasopressin release was associated with an increase in neurohypophysial cAMP content, whereas tissue cAMP remained unchanged when hormone release was potentiated.

cAMP was released in large amounts from the unstimulated neurohypophyses, whereas the efflux of this nucleotide was markedly reduced when the tissue was depolarized with excess potassium.

Tissue cAMP contents were similar in the stimulated and unstimulated glands. The efflux of cAMP was dependent on the presence of extracellular calcium.Theophylline enhanced calcium efflux from neurohypophysial tissue primarily by acting on an extracellularly bound pool of calcium.

cAMP released from neurohypophysial tissue may have an important role in regulating calcium fluxes and determining the state of activation of the neurosecretory nerve endings. (Endocrinology 106: 842, 1980)

Footnotes

^* This work was supported by MRC Grant MT₃911 and a MRC Studentship (to R.M.).

Received April 13, 1979.