Rawlings S R, Piuz I, Schlegel W, Bockaert J, Journot L
Fondation pour Recherches Médicales, University of Geneva, Switzerland.
Endocrinology. 1995 May;136(5):2088-98. doi: 10.1210/endo.136.5.7720658.
Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are hypothalamic factors believed to play a role in the regulation of anterior pituitary cell function. However, little is known about the expression of PACAP/VIP receptor (PVR) subtypes in such cells. Three PVR subtypes have recently been cloned: the PACAP-selective PVR1, and PVR2 and PVR3, which exhibit similar affinities for PACAP and VIP. In the present study we used the reverse transcription-polymerase chain reaction with PVR-specific primers to identify the PVR messenger RNAs (mRNAs) expressed in the somatotroph-like GH4C1 and the gonadotroph-like alpha T3-1 cell lines. In parallel, the effects of PACAP and VIP on intracellular signaling were studied. GH4C1 cells were found to express mRNA only for the PVR3, and neither PVR1 nor PVR2 mRNA was found. PACAP and VIP stimulated Ca2+ influx responses in individual GH4C1 cells and were equipotent in stimulating cAMP production (EC50, 15 nM) in GH4C1 cell populations, but failed to stimulate inositol phospholipid (PI) turnover, results consistent with the expression of a PVR3. In contrast, alpha T3-1 cells expressed mRNA for PVR1 and PVR3, but not PVR2. The predominant splice variant forms of PVR1 observed were PVR1s and PVR1hop, although the other forms (PVR1hiphop and PVR1hip) were also seen at much lower levels. PACAP stimulated a Ca2+ store-dependent Ca2+ spike and a sustained Ca2+ influx in individual alpha T3-1 cells, whereas VIP only stimulated Ca2+ influx. PACAP (EC50, 3 nM) was approximately 1000-fold more potent than VIP (EC50, approximately 3 microM) in stimulating cAMP production. PACAP also stimulated PI turnover (EC50, approximately 20 nM), whereas VIP stimulated PI turnover only at very high (10 microM) concentrations. These results are indicative of the expression of a PVR1. Rat anterior pituitary tissue expressed mRNAs for PVR1, PVR3, and low levels of PVR2. The coexpression of different PVRs in the same cell type and the differential expression of PVRs in different cell types would allow for a complex regulation of anterior pituitary gland function by PACAP and VIP.
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，被认为在垂体前叶细胞功能调节中发挥作用。然而，关于这些细胞中PACAP/VIP受体（PVR）亚型的表达情况却知之甚少。最近克隆出了三种PVR亚型：PACAP选择性的PVR1，以及对PACAP和VIP具有相似亲和力的PVR2和PVR3。在本研究中，我们使用针对PVR的特异性引物进行逆转录-聚合酶链反应，以鉴定在生长激素样GH4C1细胞系和促性腺激素样αT3-1细胞系中表达的PVR信使核糖核酸（mRNA）。同时，研究了PACAP和VIP对细胞内信号传导的影响。发现GH4C1细胞仅表达PVR3的mRNA，未发现PVR1和PVR2的mRNA。PACAP和VIP刺激单个GH4C1细胞中的Ca2+内流反应，并且在刺激GH4C1细胞群体中的cAMP产生方面效力相当（半数有效浓度[EC50]，15 nM），但未能刺激肌醇磷脂（PI）周转，这些结果与PVR3的表达一致。相比之下，αT3-1细胞表达PVR1和PVR3的mRNA，但不表达PVR2的mRNA。观察到的PVR1的主要剪接变体形式是PVR1s和PVRhop，尽管其他形式（PVR1hiphop和PVR1hip）也以低得多的水平出现。PACAP刺激单个αT3-1细胞中的Ca2+储存依赖性Ca2+尖峰和持续的Ca2+内流，而VIP仅刺激Ca2+内流。在刺激cAMP产生方面，PACAP（EC50，3 nM）的效力比VIP（EC50，约3 μM）强约1000倍。PACAP还刺激PI周转（EC50，约20 nM），而VIP仅在非常高的浓度（10 μM）下刺激PI周转。这些结果表明存在PVR1的表达。大鼠垂体前叶组织表达PVR1、PVR3的mRNA以及低水平的PVR2的mRNA。同一细胞类型中不同PVR的共表达以及不同细胞类型中PVR的差异表达，将使PACAP和VIP对垂体前叶功能进行复杂的调节。
