© 1983 by The Society for Integrative and Comparative Biology
Evolution of Neurohypophyseal Hormone Actions in Vertebrates1
Department of Pharmacology, Texas Tech University Health Sciences Center Lubbock, Texas 79430
Department of Pharmacology, College of Physicians and Surgeons of Columbia University New York, New York 10032
Arginine vasotocin (AVT) is one neurohypophyseal principle that has been found in all vertebrates including the cyclostomes. Although many effects have been seen with administered AVT in many vertebrate species, the physiological role of endogenous AVT is largely unknown. In this review, the evolution of the renal and vascular actions of AVT are discussed. Injection of AVT produces diuresis in teleosts and lungfishes, but antidiuresis in tetrapods. In fishes and all tetrapods except birds, AVT is hypertensive. We have proposed that the renal responses can in fact be explained by the vascular responses. In our hypothesis, there are four types of responses to AVT. In type I, the peripheral vasculature is more responsive to AVT than the renal preglomerular arteriole so that AVT will cause a significant rise in systemic blood pressure and a net increase in the glomerular perfusion. This will then result in diuretic and pressor responses. Teleosts and lungfishes belong to this type. Type 11 is exemplified by the mudpuppy which responds to AVT with antidiuresis and blood pressure increase. This can be explained by an increase in sensitivity to AVT by the preglomerular arteriole so that AVT will cause a decrease in glomerular perfusion even when systemic blood pressure is increased. In type III which can be seen in the bullfrog, the vascular response to AVT will produce glomerular antidiuresis and blood pressure increase. In addition, tubular receptors for AVT are also present and these receptors are involved in the tubular reabsorption of water, thus enhancing the antidiuretic response. Type IV as seen in mammals is mainly a tubular antidiuretic response to ADH. Evidence in support of this hypothesis is given in the paper. The above discussion concerns the renal and vascular actions of exogenous AVT. Our studies so far indicate that endogenous AVT is not the major regulatory mechanism in renal and vascular functions of the lungfish or bullfrog, although it may have a modulatory role.