CALCIUM RATHER THAN CYCLIC-AMP AS THE PHYSIOLOGICAL INTRACELLULAR REGULATOR OF PROLACTIN-RELEASE
CALCIUM RATHER THAN CYCLIC-AMP AS THE PHYSIOLOGICAL INTRACELLULAR REGULATOR OF PROLACTIN-RELEASE
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DOI：
10.1159/000123109
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发表时间：
1980-01-01
影响因子：
4.1
通讯作者：
MACLEOD, RM
中科院分区：
文献类型：
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作者：
THORNER, MO;HACKETT, JT;MACLEOD, RM
利用体外技术对泌乳素释放机制进行了研究。在胰蛋白酶的作用下，采用机械方法制备大鼠垂体前叶细胞。这些洗过的细胞与生物凝胶基质一起被抽成一个小柱，并灌注厄尔碱性盐溶液。然后在短时间间隔内收集含有PRL的洗脱液。在灌注介质中加入试验物质，测定其对PRL释放的影响。将这些研究结果与在Medium 199中培养半垂体腺所获得的结果进行比较，以测量测试物质对放射免疫可测定PRL释放的影响。多巴胺[DA]灌注分散的垂体细胞可在3分钟内明显抑制PRL的释放，并在开始灌注后11分钟达到最大抑制。停药后，PRL释放在1分钟内开始恢复，并在6.5分钟时继续上升至基线的80%。垂体细胞在不含Ca的培养基中浸润后，PRL的释放也明显减少，在细胞再次暴露于Ca后，PRL的释放得到恢复。-氨基丙基]-3,4,5-三甲氧基苯乙腈]等阻断Ca通道的药剂，也可引起PRL释放的可逆抑制。研究了离子载体A23187和X537A对PRL释放的影响。Ca离子载体A23187的存在不影响催乳素的释放，但它逆转了da介导的PRL释放抑制。在没有Ca的情况下，两个离子载体都刺激了PRL。钠通道阻滞剂河豚毒素对PRL释放无影响。前列腺素E1和霍乱毒素使cAMP水平升高，但与PRL释放模式无正相关。Gpp (NH) p [5 " -guanylyl.beta.可以利用。DA对垂体前叶组织匀浆中-咪啶二磷酸刺激的腺苷酸环化酶活性没有影响。垂体周围腺添加二丁基cAMP刺激PRL释放，半垂体添加茶碱完全逆转DA对PRL释放的抑制作用，并引起cAMP水平升高。强直性高水平的PRL释放可能是通过细胞外钙的流入来维持的，而DA抑制了这一过程。细胞内cAMP的作用尚不明确；二丁基cAMP和茶碱的作用可能是由于细胞内Ca的动员，从而通过这种机制而不是通过cAMP刺激PRL的释放。正常乳变性物分泌PRL的调节显然是一个钙介导的过程。
Studies on the mechanisms which govern prolactin [PRL] release were undertaken using 2 in vitro techniques. A dispersed preparation of rat anterior pituitary cells was made by mechanical means in the presence of trypsin. These washed cells were drawn up into a small column together with a Bio-Gel matrix and perfused with Earle''s basic salt solution. The eluates containing PRL were then collected at short intervals. Test substances were added to the perfusion medium and their effect on PRL release was measured. The results of these studies were compared with those obtained by incubating hemipituitary glands in Medium 199 to measure the effect of test substances on the release of radioimmunoassayable PRL. Perifusion of dispersed pituitary cells with dopamine [DA] produced a marked inhibition of PRL release within 3 min, and maximal suppression 11 min after initiating the perifusion. Upon withdrawal of DA, PRL release began to recover within 1 min and continued to rise to 80% of baseline at 6.5 min. Perifusion of pituitary cells in medium free of Ca also produced a marked reduction in PRL release which was restored after reexposure of the cells to Ca. The addition of Mn and D-600 [.alpha.-isopropyl-.alpha.-[N-methyl-N-homoveratryl-.gamma.-aminopropyl]-3,4,5-trimethoxyphenylacetonitrile], agents which block Ca channels, also caused reversible inhibition of PRL release. The effects of the ionophores A23187 and X537A on PRL release were studied. The presence of Ca ionophore A23187 did not effect prolactin release but it reversed the DA-mediated inhibition of PRL release. In the absence of Ca, both ionophores stimulated PRL. Tetrodotoxin, a Na channel blocker, had no effect on PRL release. Agents such as prostaglandin E1 and cholera toxin increased cAMP levels, but no positive correlation was obtained on PRL release patterns. Gpp(NH)p[5''-guanylyl.beta.-.gamma.-imidodiphosphate]-stimulated adenylate cyclase activity in homogenates of anterior pituitary tissue was unaffected by DA. Addition of dibutyryl cAMP to perifused pituitary glands stimulated PRL release and theophylline added to hemipituitary gland completely reversed the inhibitory effect of DA on PRL release, and caused a concomitant increase in cAMP levels. The tonic high level of PRL release may be maintained by influx of extracellular Ca, and DA inhibits this process. The role of intracellular cAMP is undefined; the effects of dibutyryl cAMP and theophylline may be due to mobilization of intracellular Ca and thereby stimulate PRL release by this mechanism rather than through cAMP. Regulation of PRL secretion by normal lactotropes is evidently a Ca-mediated process.