Gap junctional intercellular communication of bovine granulosa and thecal cells from antral follicles: effects of luteinizing hormone and follicle-stimulating hormone.

Throughout each estrous cycle, the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), are involved in regulation of folliculogenesis. We have shown that LH or FSH affect cellular interactions mediated by gap junctions in bovine granulosa and thecal cells in vitro. To evaluate further the hypothesis that gonadotropins influence gap junctional intercellular communication (GJIC) and expression of gap junctional proteins known as connexins (Cx), throughout antral follicle development, granulosa and thecal cells from large (>10 mm; n = 13), medium (5-10 mm; n = 20), and small (<5 mm; n = 27) follicles were cultured (n = 4 cultures per size) with or without LH, FSH, or LH + FSH for 24 h. GJIC was evaluated (n = 125-150 cells/treatment group) by using the fluorescent recovery after photobleaching technique and laser cytometry. Additionally, Cx43, Cx32, and Cx26 were detected in cultured cells by immunocytochemistry and Cx43 by Western immunoblot analysis. Finally, progesterone production by cultured cells was evaluated by radioimmunoassay. Across all follicles and treatments, GJIC was greater (p < 0.01) for granulosa than thecal cells (4.9 +/- 0.05 vs 3.8 +/- 0.04%/min). For granulosa cells of large and medium follicles, LH and/or FSH did not affect GJIC. For granulosa cells of small follicles, FSH increased (p < 0.05), but LH or LH + FSH had no effect on GJIC. For thecal cells of large follicles, LH increased (p < 0.01) GJIC, whereas FSH or LH + FSH had no effects. For thecal cells of medium and small follicles, LH and/or FSH did not affect GJIC. These results demonstrate that FSH influenced GJIC of granulosa cells from small, but not from medium or large, follicles, and LH influenced GJIC of thecal cells from large, but not from medium or small, follicles. Cx43 was present as punctate staining between granulosa or thecal cells from all cultures, indicating assembled gap junctions. LH + FSH increased (p < 0.05) expression of Cx43 only by thecal cells from large follicles. Cx32 was detected in the perinuclear cytoplasm of cultured granulosa or thecal cells, and in the cytoskeleton of a few cells per culture dish in all sizes of follicles. Cx26 was present in a regular pattern throughout the cytoplasm of granulosa or thecal cells in all sizes of follicles. For granulosa cells from large follicles, progesterone production was stimulated (p < 0.05) with LH or FSH alone but was unaffected by LH + FSH. For granulosa cells from medium and small follicles, progesterone production was unaffected by LH and/or FSH. For thecal cells from all sizes of follicles, LH, FSH, and LH + FSH stimulated (p < 0.05) production of progesterone. These data indicate that LH and FSH influence gap junction function and expression, which likely contributes to the development and maintenance of ovarian follicles.