Regulation of vasopressin secretion.

With the development of sensitive and specific radio-immunoassays to measure the low circulating concentrations of vasopressin there has been a quantum leap in our understanding of the physiological processes involved in the regulation of its secretion. The results of Verney's pioneering studies in dogs led to the concept of 'osmoreceptors'. It is now appreciated that osmoregulation of vasopressin release is of principal importance in the maintenance of water balance. Functional characteristics of the osmoregulatory system have been defined clearly by independent laboratories, and more recently the physiological influences that can subtly alter this very finely controlled system have been described. Non-osmotic factors that release vasopressin have been recognized for many years. Secretion of vasopressin in response to haemodynamic influences has been characterized, and significant hypotension and/or hypovolaemia are potent stimuli to hormone release. Other non-osmotic factors--nausea/emesis, hypoglycaemia--may play important roles in disturbances of water balance. Vasopressin should not, however, be regarded as a stress hormone, since recent careful studies in a variety of species indicate that secretion is not enhanced following a series of different noxious stimuli.