Apelin and vasopressin: two work better than one.

Summary Water retention in the kidney is known to be an active phenomenon, controlled by a neuropeptide: vasopressin. Water excretion was assumed to be a passive phenomenon, as a result of vasopressin release blockade. This simplistic view is incorrect because water excretion is also controlled by a diuretic neuropeptide, apelin, produced not only by several peripheral tissues, but also by hypothalamic neurones, in particular the vasopressin ones projecting to the posterior pituitary.