CELL-TO-CELL COMMUNICATION IN THE ANTERIOR-PITUITARY - EVIDENCE FOR GAP JUNCTION-MEDIATED EXCHANGES BETWEEN ENDOCRINE-CELLS AND FOLLICULOSTELLATE CELLS

The ability of rat anterior pituitary cells to communicate through gap junctions (GJ) was studied using a fluorescent molecule, Lucifer Yell ow (LY), which freely passes through GJ channels. The probe was introd uced into the cell cytoplasm by using either the cut-end loading metho d on intact tissue, or cell microinjection on cultured cells. The iden tification of communicating cells was performed by immunofluorescence labeling of specific hormones in endocrine cells and of S100 protein i n folliculostellate (FS) cells, Rat anterior pituitary cells in their physiological organization, i.e. in the intact tissue, exhibited a hig h level of coupling through GJ, LY-labeled cells were found up to 300- mu m apart from its site of introduction. The communicating cells were primarily PRL cells, GH cells, and FS cells. Only a few LH, TSH, and ACTH cells were labeled with LY. Anterior pituitary cells, isolated fr om the rat tissue by mild protease treatment and cultured for 3 days, reestablished functional GJ as demonstrated by microinjection of LY in to individual cells. By immunolabeling of specific hormones and/or S10 0 protein, we found a GJ coupling between FS cells, and between FS cel ls and endocrine cells, including PRL cells. The communication between FS cells was by far the most frequent. In conclusion, we demonstrate the presence of functional GJ between anterior pituitary cells of the same type and between anterior pituitary cells having distinct differe ntiated functions.