Vitale M L, Cardin J, Gilula N B, Carbajal M E, Pelletier R M
Département de Pathologie et biologie cellulaire, Faculté de Médecine, Université of Montréal, 2900 Edouard-Montpetit, Montréal, Québec, Canada H3T 1J4.
Biol Reprod. 2001 Feb;64(2):625-33. doi: 10.1095/biolreprod64.2.625.
Because in mammals the anterior pituitary lacks innervation, we investigated whether gap junctions established between selected cells within the gland are part of an intrapituitary mechanism to ensure physiological synchronization of cells involved in the control of hormone secretion. We report here the dynamics of anterior pituitary connexin 43 (Cx43)-gap junctions throughout the mink (Mustela vison) annual reproductive cycle and its relationship with the anterior pituitary prolactin (PRL) content that parallels variations in serum PRL levels documented in the literature. We found that PRL anterior pituitary levels were maximal in spring and during lactation and that they were minimal in autumn and winter. Anterior pituitary Cx43 levels were maximal during periods of high PRL secretion. During these periods, Cx43-positive gap junctions localized to stellate-shaped cells occupying the center of anterior pituitary follicles and to the rounded cells occupying the remaining follicles. Connexin 43-positive gap junctions were also observed between adjacent follicles. During periods of low PRL pituitary content, Cx43-positive gap junctions localized to the stellate cells but not to the cells of the remaining follicles. Moreover, Cx43 labeling was undetected between adjacent follicles. To assess between which cells within the mink anterior pituitary the Cx43 gap junctions were established, the different anterior pituitary cell populations were separated by a discontinuous Percoll gradient, and Western blot analyses of each cell population using Cx43 antibodies were performed. The immunoblots showed a Cx43 immunoreactive band associated with the cell layer enriched in S-100-positive, stellate-shaped cells. The result was confirmed by fluorescence microscopy studies that showed that Cx43-mediated gap junctions were established preferentially between the cultured S-100-positive, elongated cells. The results show that in mink stellate cells, the junctional machinery associated with the Cx43 protein varies in synchrony with the anterior pituitary PRL content throughout the mink annual reproductive cycle. It is suggested that the Cx43 gap junctions on the stellate cells play an important role in the synchronization of cellular activity within selected follicles of the anterior pituitary, thus contributing to the control of PRL secretion during the annual reproductive cycle.
由于在哺乳动物中腺垂体缺乏神经支配，我们研究了腺体内特定细胞之间建立的缝隙连接是否是腺垂体内确保参与激素分泌控制的细胞生理同步化机制的一部分。我们在此报告水貂（鼬属）全年生殖周期中腺垂体连接蛋白43（Cx43）-缝隙连接的动态变化及其与腺垂体催乳素（PRL）含量的关系，PRL含量与文献中记载的血清PRL水平变化平行。我们发现腺垂体PRL水平在春季和哺乳期最高，而在秋季和冬季最低。腺垂体Cx43水平在PRL高分泌期最高。在这些时期，Cx43阳性缝隙连接定位于占据腺垂体滤泡中心的星状细胞以及占据其余滤泡的圆形细胞。在相邻滤泡之间也观察到了连接蛋白43阳性缝隙连接。在PRL腺垂体含量低的时期，Cx43阳性缝隙连接定位于星状细胞，但不定位于其余滤泡的细胞。此外，在相邻滤泡之间未检测到Cx43标记。为了评估水貂腺垂体中哪些细胞之间建立了Cx43缝隙连接，通过不连续的Percoll梯度分离不同的腺垂体细胞群，并使用Cx43抗体对每个细胞群进行蛋白质印迹分析。免疫印迹显示与富含S-100阳性星状细胞的细胞层相关的Cx43免疫反应条带。荧光显微镜研究证实了该结果，该研究表明Cx43介导的缝隙连接优先在培养的S-100阳性细长细胞之间建立。结果表明，在水貂星状细胞中，与Cx43蛋白相关的连接机制在水貂全年生殖周期中与腺垂体PRL含量同步变化。提示星状细胞上的Cx43缝隙连接在腺垂体特定滤泡内的细胞活动同步化中起重要作用，从而有助于在全年生殖周期中控制PRL分泌。
