Arginine Vasopressin (AVP) and AVP-Like Immunoreactivity in Peripheral Tissues

THE NONAPEPTIDE arginine vasopressin (AVP) is classically synthesized as part of a precursor hormone [AVP-neurophysin II, (AVP-NPII)] in the magnocellular neurons of the supraoptic and paraventricular nuclei of the hypothalamus. It is then transported via their axons to the posterior pituitary, where it is secreted into the circulation (1). AVP, which has both antidiuretic and pressor effects, regulates water clearance in the kidney as well as blood pressure. In addition, AVP, together with CRF, has been shown to be involved in the regulation of ACTH secretion from the anterior pituitary (2–5). Furthermore, AVP has also been implicated in learning and memory (6, 7), central cardiovascular regulation (8–11), and other central nervous system functions (7, 12–14). Recently, the presence of many neuropeptides, including AVP, has been demonstrated in a number of peripheral, mainly endocrine tissues, largely on immunochemical criteria. Thus, this review is concerned with the demonstration of immunoreactive (ir)-AVP in the periphery. In addition, in reviewing current knowledge regarding cellular localization, molecular species, possible gene expression/synthesis and function at these sites, we will attempt to establish whether these AVP-like peptides are authentic AVP.