Saunders S L, Reifel C W, Shin S H
Acta Anat (Basel). 1982;114(1):74-80. doi: 10.1159/000145580.
Lactotrophs in the adenohypophysis have the apparent inherent capability to produce simultaneous secretion of prolactin from individual cells. There are two possibilities to account for this synchronized, discrete pulsatile secretion: (1) humoral communication, or (2) cell-to-cell syncytial communication. As a first step in examining the second possibility, we searched for ultrastructural evidence of intercellular contacts. The presence of desmosomes, the conventional junctions that serve to anchor adjacent cells, would be the first step in proving contact between homologous cells. In order to increase the observation of desmosomes, the population of lactotrophs in the adenohypophysis was increased by implantation of capsules containing estradiol in male Sprague-Dawley rats. The adenohypophyses were then examined by electron microscopy for indications of these intercellular bridges. Desmosomes were discovered between lactotrophs, indicating that cell-to-cell contact does exist, and suggesting that the desmosome may help the formation of a syncytium among lactotrophs, either directly or indirectly. Since an ectopic pituitary without direct help from the hypothalamus can secrete prolactin in a pulsatile fashion and since there are desmosomes between lactotrophs, it is possible that the synchronized prolactin release occurs through a direct cell-to-cell communication system which is linked by the desmosomes.
腺垂体中的催乳素细胞具有从单个细胞同时分泌催乳素的明显内在能力。对于这种同步的、离散的脉冲式分泌，有两种可能的解释：（1）体液通讯，或（2）细胞间的合胞体通讯。作为研究第二种可能性的第一步，我们寻找细胞间接触的超微结构证据。桥粒的存在，即用于锚定相邻细胞的传统连接结构，将是证明同源细胞之间存在接触的第一步。为了增加对桥粒的观察，通过在雄性斯普拉格-道利大鼠体内植入含雌二醇的胶囊来增加腺垂体中催乳素细胞的数量。然后通过电子显微镜检查腺垂体，寻找这些细胞间连接的迹象。在催乳素细胞之间发现了桥粒，这表明细胞间接触确实存在，并提示桥粒可能直接或间接地有助于催乳素细胞之间形成合胞体。由于异位垂体在没有下丘脑直接帮助的情况下也能以脉冲方式分泌催乳素，并且由于催乳素细胞之间存在桥粒，所以同步的催乳素释放有可能通过由桥粒连接的直接细胞间通讯系统发生。
