Origin and fate of cytoplasmic gap junctional vesicles in rabbit granulosa cells.

Vesicles within the cytoplasm of the rabbit granulosa cell, in both thin section and freeze-fracture preparations, appear to consist of typical gap junctional membrane. In most cases these vesicles, like gap junctions at the cell surface, are composed of two membranes, but in rare cases may consist in part of single membrane, identified as gap junctional because of the presence of typical 8.5 nm P face particles and E face pits. Both thin section and freeze-fracture studies support the view that these vesicles may be produced by the endocytosis of junctional membrane from the cell surface as one cell invaginates into its neighbor at the junction. The presence of apparent acid phosphatase activity within the matrix of these gap junctional vesicles suggests that they may represent a stage in the specific degradation of gap junctional membrane.