Hezareh M, Schlegel W, Rawlings S R
Fondation pour Recherches Médicales, University of Geneva, Switzerland.
J Neuroendocrinol. 1996 May;8(5):367-74. doi: 10.1046/j.1365-2826.1996.04645.x.
Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are hypothalamic factors that play roles in the regulation of anterior pituitary cell activity. PACAP exists in 2 forms physiologically, a 38 amino acid form (PACAP38) and a form possessing the N-terminal 27 amino acids of PACAP38 (PACAP27). We have previously shown that PACAP38 stimulates an increase in [Ca2+]i in rat gonadotrophs. In an attempt to identify the PACAP receptor type underlying this effect, we compared the potency of PACAP38, PACAP27 and VIP to stimulate Ca2+ changes in identified single rat gonadotrophs. All 3 peptides at 100 nM were capable of stimulating high amplitude Ca2+ oscillations, which were also observed in the absence of extracellular Ca2+. The order of potency of these peptides was PACAP38 > PACAP27 > VIP, and a potent antagonist of the PACAP/VIP type II binding site ([4-CI-D-Phe6, Leu17]-VIP) failed to block these responses, suggesting that these effects are mediated through a PACAP/VIP type 1 receptor (PVR1). The Ca2+ responses to PACAP38 and VIP were unaffected by overnight treatment of the cells with pertussis toxin (PTX; 250 ng/ml) indicating that these responses are mediated by a PTX-insensitive G-protein. Finally, the Ca2+ responses stimulated by PACAP38 and VIP were blocked by the phospholipase C-beta blocker U73122 (5 microM). In summary, PACAP stimulates Ca2+ oscillations in rat gonadotrophs through the activation of the PVR1 linked to a PTX-insensitive G-protein and the activation of phospholipase C-beta. VIP can stimulate the same pathway in rat gonadotrophs, although it is at least 100 fold less potent than PACAP38.
垂体腺苷酸环化酶激活多肽（PACAP）和血管活性肠肽（VIP）是下丘脑因子，在前垂体细胞活性调节中发挥作用。PACAP在生理上以两种形式存在，一种是38个氨基酸的形式（PACAP38），另一种是具有PACAP38 N端27个氨基酸的形式（PACAP27）。我们之前已经表明，PACAP38可刺激大鼠促性腺激素细胞内[Ca2+]i增加。为了确定这种作用背后的PACAP受体类型，我们比较了PACAP38、PACAP27和VIP刺激已鉴定的单个大鼠促性腺激素细胞内Ca2+变化的效力。100 nM的所有三种肽都能够刺激高幅度的Ca2+振荡，在无细胞外Ca2+的情况下也能观察到这种振荡。这些肽的效力顺序为PACAP38 > PACAP27 > VIP，并且PACAP/VIP II型结合位点的强效拮抗剂（[4-CI-D-Phe6, Leu17]-VIP）未能阻断这些反应，这表明这些作用是通过PACAP/VIP 1型受体（PVR1）介导的。用百日咳毒素（PTX；250 ng/ml）对细胞进行过夜处理后，对PACAP38和VIP的Ca2+反应未受影响，这表明这些反应是由对PTX不敏感的G蛋白介导的。最后，PACAP38和VIP刺激的Ca2+反应被磷脂酶C-β阻滞剂U73122（5 microM）阻断。总之，PACAP通过激活与对PTX不敏感的G蛋白相连的PVR1以及激活磷脂酶C-β来刺激大鼠促性腺激素细胞内的Ca2+振荡。VIP也能在大鼠促性腺激素细胞中刺激相同的途径，尽管其效力比PACAP38至少低100倍。
