Schofield J G, Khan A I, Wood A
Department of Biochemistry, Medical School, University of Bristol.
J Endocrinol. 1988 Mar;116(3):393-401. doi: 10.1677/joe.0.1160393.
Acetylcholine is known to stimulate the secretion of growth hormone and prolactin and the efflux of 86Rb from bovine anterior pituitary cells: dopamine prevents the stimulation of 86Rb efflux and of prolactin but not growth hormone secretion. The sensitivity of these responses to pertussis toxin has been determined. Treatment of bovine anterior pituitary cells in primary culture with pertussis toxin (18 h, 100 ng/ml) did not modify the stimulation of prolactin secretion by acetylcholine, but prevented its inhibition by dopamine. In lactotrophs, dopamine but not acetylcholine receptors are therefore coupled to secretion through a pertussis toxin substrate. The stimulation of 86Rb efflux by acetylcholine was also unaffected by pertussis toxin and, again, its inhibition by dopamine was prevented. Treatment of the cells with pertussis toxin enhanced the secretion of growth hormone in response to acetylcholine. Nitrendepine (1 mumol/l) prevented the cholinergic stimulation of growth hormone but not prolactin secretion from these cells. Acetylcholine increased the cytoplasmic calcium concentration and this rise was enhanced by treatment of the cells with pertussis toxin. Nitrendepine partially inhibited the rise in calcium caused by acetylcholine, and prevented the enhancement of the rise following pertussis toxin treatment. Cholinergic stimulation of growth hormone therefore depends on calcium entry through nitrendepine-sensitive channels, whereas stimulation of prolactin secretion does not, and in somatotrophs a pertussis toxin substrate may limit calcium entry through these channels. These different sensitivities of somatotrophs and lactotrophs to pertussis toxin and nitrendepine may reflect differences in the properties of the predominant calcium currents in the two cell types.
已知乙酰胆碱可刺激生长激素和催乳素的分泌以及86Rb从牛垂体前叶细胞流出：多巴胺可阻止86Rb流出和催乳素分泌的刺激，但不影响生长激素的分泌。已确定这些反应对百日咳毒素的敏感性。用百日咳毒素（18小时，100纳克/毫升）处理原代培养的牛垂体前叶细胞，并未改变乙酰胆碱对催乳素分泌的刺激，但阻止了多巴胺对其的抑制。因此，在催乳细胞中，多巴胺受体而非乙酰胆碱受体通过百日咳毒素底物与分泌偶联。乙酰胆碱对86Rb流出的刺激也不受百日咳毒素影响，同样，多巴胺对其的抑制也被阻止。用百日咳毒素处理细胞增强了生长激素对乙酰胆碱的反应性分泌。尼群地平（1微摩尔/升）阻止了这些细胞中乙酰胆碱对生长激素的刺激，但不影响催乳素的分泌。乙酰胆碱增加了细胞质钙浓度，用百日咳毒素处理细胞可增强这种升高。尼群地平部分抑制了乙酰胆碱引起的钙升高，并阻止了百日咳毒素处理后钙升高的增强。因此，乙酰胆碱对生长激素的刺激取决于通过尼群地平敏感通道的钙内流，而对催乳素分泌的刺激则不然，在生长激素细胞中，百日咳毒素底物可能会限制通过这些通道的钙内流。生长激素细胞和催乳细胞对百日咳毒素和尼群地平的这些不同敏感性可能反映了两种细胞类型中主要钙电流特性的差异。
