Vasoactive intestinal peptide and renin secretion.

VIP has now been shown to produce an increase in renin release in a number of species, including humans. Our work suggests that VIP is capable of producing this effect by a direct action on the renin-secreting juxtaglomerular cells of the kidney. We have found no evidence to support the possibility that VIP produces this effect as a neurotransmitter in the kidney. In this regard, it should be noted that VIP has been identified as a cotransmitter primarily in cholinergic neurons. The kidney is thought to lack cholinergic innervation, and acetylcholine has no effect on renin secretion. We have explored two conditions where renin secretion is known to increase and found that circulating levels of VIP did not increase along with the increase in PRA. Thus, at least in hemorrhage and dietary sodium restriction, VIP does not appear to affect renin secretion through a humoral mechanism. There could be other untested situations where a humoral effect of VIP might come into play since we have shown that the whole animal is capable of increasing plasma VIP to levels that affect renin release. Studies employing recently developed VIP antagonists have the potential to determine in which physiological or pathological situations VIP contributes to the control of renin secretion. For example, in endotoxic shock, plasma levels of both VIP and PRA are significantly elevated. Could the increase in PRA be partly dependent on an action of circulating VIP?