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垂体激素分泌对自发性电压门控钙内流模式的依赖性。细胞类型特异性动作电位分泌偶联。

Dependence of pituitary hormone secretion on the pattern of spontaneous voltage-gated calcium influx. Cell type-specific action potential secretion coupling.

作者信息

Van Goor F, Zivadinovic D, Martinez-Fuentes A J, Stojilkovic S S

机构信息

Endocrinology and Reproduction Research Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.

出版信息

J Biol Chem. 2001 Sep 7;276(36):33840-6. doi: 10.1074/jbc.M105386200. Epub 2001 Jul 16.

Abstract

In excitable cells, voltage-gated calcium influx provides an effective mechanism for the activation of exocytosis. In this study, we demonstrate that although rat anterior pituitary lactotrophs, somatotrophs, and gonadotrophs exhibited spontaneous and extracellular calcium-dependent electrical activity, voltage-gated calcium influx triggered secretion only in lactotrophs and somatotrophs. The lack of action potential-driven secretion in gonadotrophs was not due to the proportion of spontaneously firing cells or spike frequency. Gonadotrophs exhibited calcium signals during prolonged depolarization comparable with signals observed in somatotrophs and lactotrophs. The secretory vesicles in all three cell types also had a similar sensitivity to voltage-gated calcium influx. However, the pattern of action potential calcium influx differed among three cell types. Spontaneous activity in gonadotrophs was characterized by high amplitude, sharp spikes that had a limited capacity to promote calcium influx, whereas lactotrophs and somatotrophs fired plateau-bursting action potentials that generated high amplitude calcium signals. Furthermore, a shift in the pattern of firing from sharp spikes to plateau-like spikes in gonadotrophs triggered luteinizing hormone secretion. These results indicate that the cell type-specific action potential secretion coupling in pituitary cells is determined by the capacity of their plasma membrane oscillator to generate threshold calcium signals.

摘要

在可兴奋细胞中,电压门控钙内流为胞吐作用的激活提供了一种有效机制。在本研究中,我们证明,尽管大鼠垂体前叶催乳素细胞、生长激素细胞和促性腺激素细胞表现出自发性且依赖细胞外钙的电活动,但电压门控钙内流仅在催乳素细胞和生长激素细胞中触发分泌。促性腺激素细胞中缺乏动作电位驱动的分泌并非由于自发放电细胞的比例或动作电位频率。在长时间去极化期间,促性腺激素细胞表现出与生长激素细胞和催乳素细胞中观察到的信号相当的钙信号。所有三种细胞类型中的分泌囊泡对电压门控钙内流也具有相似的敏感性。然而,三种细胞类型中动作电位钙内流的模式有所不同。促性腺激素细胞中的自发活动以高幅度、尖锐的动作电位为特征,其促进钙内流的能力有限,而催乳素细胞和生长激素细胞产生平台爆发性动作电位,从而产生高幅度钙信号。此外,促性腺激素细胞中动作电位发放模式从尖锐动作电位向平台样动作电位的转变触发了促黄体生成素的分泌。这些结果表明,垂体细胞中细胞类型特异性的动作电位分泌偶联是由其质膜振荡器产生阈值钙信号的能力决定的。

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