GAP JUNCTION OF STRATUM-GRANULOSUM CELLS OF MOUSE FOLLICLES - IMMUNOHISTOCHEMISTRY AND ELECTRON-MICROSCOPY

The gap junction (GJ) of stratum granulosum cells was investigated in growing and mature follicles of the mouse by means of light- and elect ron-microscopic immunohistochemistry, freeze-fracturing and deep-etchi ng methods. GJ increased in number and size in concert with the progre ss of follicular maturation and decreased rapidly in the preovulatory mature follicle. GJ membrane showed invagination, most remarkably at 5 h after hCG injection, within the cytoplasm of the granulosum cell. T wo types of internalization seemed possible, annular internalization a nd highly convoluted tubular invagination, both by an actin-mediated m echanism. At least, a part of the internalized GJ membrane seemed to b e degraded by a certain lysosomal enzyme (s). Connexin43 (derived from rat cardiac muscle GJ) was indicated to be a constituent of GJ protei n in the mouse stratum granulosum cell. There was no GJ particle coexi sting with tight junctional strands; by contrast, a formation plaque a ppeared quite often on granulosum cells at various stages. Such a plaq ue is presumed to represent a precursor structure of the new GJ of the se cells. So far examined, however, the formation plaque failed to sho w positive reaction against anti-Cx43 antibody.