Stimulation of <i>in vitro </i>Prolactin Release by Vasoactive Intestinal Peptide

Abstract

VIP stimulated prolactin secretion from incubated rat hemipituitaries. Under the same conditions, the secretion of GH, LH, FSH was not affected. The stimulation of prolactin was dose-dependent, with an apparent affinity of VIP of 10.9 ± 3.1 nM and a maximal stimulation of 57.7 ± 4.2%. Secretin, a structurally related peptide, was also active at higher concentrations whereas another partial analogue, glucagon, was ineffective. The effect of VIP was not blocked by α-flupentixol, a potent dopaminergic antagonist, at concentrations which antagonized the dopamine inhibition of prolactin secretion. Stimulation by VIP and TRH was additive. Neither Metenkephalin nor naloxone interfered with the response to VIP. It thus seems that specific VIP receptors are present on pituitary prolactin cells. VIP, present in the mediobasal hypothalamus and detected in the hypothalamo-hypophyseal portal blood therefore is a good candidate as a physiological PRF.

Pituitary Adenylate Cyclase-Activating Polypeptide and Its Receptors: 20 Years after the Discovery

“…The secretory activity of lactotrope cells is also regulated by various hypothalamic neuropeptides (Ruberg et al, 1981;Hinuma et al, 1998;Galas et al, 2009). In particular, VIP and to a lesser extent PHI and secretin stimulate PRL secretion (Vijayan et al, 1979;Enjalbert et al, 1980;Kimura et al, 1987;Muratori et al, 1994;Judd, 1995;Youngren et al, 1998). In fact, PACAP is more potent than other members of the family in stimulating PRL secretion because intrave- Miyata et al, 1989;Culler and Paschall, 1991;Canny et al, 1992;Gracia-Navarro et al, 1992;Leonhardt et al, 1992;Perrin et al, 1993;Rawlings et al, 1993;Hashizume et al, 1994;Garrel et al, 2002 Somatotrope cells 1 cAMP, 1 ͓Ca 2ϩ ͔ i 1/3 GH release Miyata et al, 1989;Canny et al, 1992;Goth et al, 1992;Gracia-Navarro et al, 1992;Hart et al, 1992;Jarry et al, 1992;Leonhardt et al, 1992;Nagy et al, 1993;Rawlings et al, 1993;Wei et al, 1993;Yada et al, 1993;Hashizume et al, 1994;Velkeniers et al, 1994;Rousseau et al, 1999;Wong et al, 2005; Miyata et al, 1989;Gracia-Navarro et al, 1992;Hart et al, 1992;Jarry et al, 1992;<...>…”

Presence of Vasoactive Intestinal Peptide Receptor in the Hen Hypothalamus.

“…The higher affinity site is at the level of 10-10 M and is thought to be the specific receptor for VIP, because the lower affinity site, which is at the level of 10.8 M, is regarded as not having the binding specificity for VIP, i.e., it binds not only to VIP but also to other peptides of similar chemical structure such as secretin and glucagon [24]. One of the physiological actions of VIP in mammals and birds is known to stimulate prolactin (PRL) release from the pituitary.…”

Dopaminergic modulation of adenylate cyclase stimulation by vasoactive intestinal peptide in anterior pituitary.

“…This peptide increases the plasma concentration ofprolactin in male (13) or ovariectomized female rats (14). In vitro, VIP activates pituitary adenylate cyclase (15) and stimulates prolactin secretion selectively (16). Thus, the VIP-sensitive adenylate cyclase could be an interesting model to ascertain whether the dopamine recognition sites of mammotrophs are coupled with adenylate cyclase.…”