Bjøro T, Wiik P, Opstad P K, Gautvik K M, Haug E
Acta Physiol Scand. 1987 Aug;130(4):609-18. doi: 10.1111/j.1748-1716.1987.tb08183.x.
Vasoactive intestinal peptide (VIP) stimulates prolactin (PRL) secretion from cultured rat pituitary cells (GH cells) (Bjøro et al. 1984). This study demonstrates the presence of specific receptors for 125I-VIP on the GH4C1 cells. Specific binding was rapid and biphasic giving a transient plateau lasting from 7 to 30 min. Thereafter specific binding declined to about one-third after 90 min. This coincided with enhanced degradation of 125I-VIP. The degradation was mainly cell-mediated and only partly receptor dependent. Trichloroacetic acid precipitation and absorption chromatography indicated that the degradation products were either 125I- and/or small labelled peptide fragments. Bioassay, RIA and rebinding studies also demonstrated degradation of VIP. Pretreatment of GH4C1 cells with trypsin decreased the rate of degradation of 125I-VIP, but also reduced the amount of specific binding. Scatchard analysis of binding data indicated the existence of two independent classes of receptors, one with Kd = 2.2 nM and Bmax = 15 fmol per 10(6) cells and another with Kd = 180 nM and Bmax = 550 fmol per 10(6) cells. The IC50 for VIP, PHI and secretin were 4, 5 and 500 nM, respectively. We conclude that the high affinity receptor is the most probable mediator of VIP on PRL secretion. The effect of VIP and PHI on PRL secretion in GH4C1 cells is mediated through one common receptor.
血管活性肠肽（VIP）可刺激培养的大鼠垂体细胞（GH细胞）分泌催乳素（PRL）（比约罗等人，1984年）。本研究证明了GH4C1细胞上存在125I-VIP的特异性受体。特异性结合迅速且呈双相性，出现一个持续7至30分钟的短暂平台期。此后，90分钟后特异性结合下降至约三分之一。这与125I-VIP降解增强相吻合。降解主要是细胞介导的，仅部分依赖受体。三氯乙酸沉淀和吸附色谱表明降解产物为125I和/或小的标记肽片段。生物测定、放射免疫分析和再结合研究也证明了VIP的降解。用胰蛋白酶预处理GH4C1细胞可降低125I-VIP的降解速率，但也减少了特异性结合量。对结合数据的Scatchard分析表明存在两类独立的受体，一类Kd = 2.2 nM，Bmax = 每10(6)个细胞15 fmol，另一类Kd = 180 nM，Bmax = 每10(6)个细胞55 fmol。VIP、PHI和促胰液素的IC50分别为4、5和500 nM。我们得出结论，高亲和力受体最有可能是VIP调节PRL分泌的介质。VIP和PHI对GH4C1细胞中PRL分泌的作用是通过一个共同受体介导的。
