Korean J Physiol Pharmacol.
1998 Aug;2(4):443-454.
Mechanism of vasoactive intestinal polypeptide-induced catecholamine
secretion from the rat adrenal medulla
- Affiliations
-
- 1Department of Pharmacology, College of Medicine, Chosun University, Kwanaiu 501-759, South Korea.
Abstract
-
The present study was attempted to investigate the effect of vasoactive
intestinal polypeptide (VIP) on secretion of catecholamines (CA) and to
establish whether there is the existence of a noncholinergic mechanism
in adrenomedullary CA secretion from the isolated perfused rat adrenal
gland. The perfusion into an adrenal vein of VIP (3 X 10-6 M) for 5 min
or the injection of acetylcholine (ACh, 5.32 X 10-3 M) resulted in
great increases in CA secretion. Tachyphylaxis to releasing effect of
CA evoked by VIP was not observed by the repeated perfusion. The net
increase in adrenal CA secretion evoked by VIP still remained
unaffected in the presence of atropine or chlorisondamine. However, the
CA release in response to ACh was greatly inhibited by the pretreatment
with atropine or chlorisondamine. The releasing effects of CA evoked by
either VIP or ACh were depressed by pretreatment with nicardipine,
TMB-8, and the perfusion of Ca2+-free medium. Moreover, VIP- as well as
ACh-evoked CA secretory responses were markedly inhibited under the
presence of (Lys1, Pro2.5, Arg3.4, Tyr6)-VIP or naloxone. CA secretory
responses induced by ACh and high K+ (5.6 X 10-2 M) were potentiated by
infusion of VIP (3 X 10-6 M for 5 min). Taken together, these
experimental results indicate that VIP causes CA release in a fashion
of calcium ion-dependence, suggesting strongly that there exists a
noncholinergic mechanism that may be involved in the regulation of
adrenomedullary CA secretion through VIP receptors in the rat adrenal
gland, and that VIP may be the noncholinergic excitatory secretagogue
present in the chromaffin cells.