The role of alpha1 (connexin-43) gap junction expression in adrenal cortical cell function.

To investigate the relationship between adrenal cell function and gap junction expression, a bovine adrenal cell line (SBAC) was studied. Western blot and immunocytochemical techniques were used to demonstrate gap junction expression in SBAC cell populations. Cells expressed alpha1 (connexin 43) gap junction protein at points of cell-to-cell contact. Gap junction number and size increased in populations treated with ACTH (40 mU/ml) or dibutyryl cAMP (DbcAMP, 1.0 mM). Treatment with either ACTH or DbcAMP increased steroid production and cAMP levels. SBAC cell number, however, decreased in ACTH- or DbcAMP-treated populations. The number of cells increased in cultures transfected with alpha1-antisense complementary DNA. Neither ACTH nor DbcAMP treatment decreased cell number or increased steroidogenesis in alpha1-antisense complementary DNA-transfected cell populations. However, cell populations in which gap junctions were inhibited retained the capacity to increase cAMP production in response to ACTH (40 mU/ml) treatment. Hormone-stimulated gapjunction expression and cell communication may represent an important factor in adrenal gland function and control of proliferation.

Characterization of gap junction expression in the adrenal gland.

To characterize the presence of gap junctions in adrenal tissue we used immunohistochemical analysis of connexin expression in whole adrenal glands and in primary rat adrenal cortical cell cultures. alpha 1 (connexin 43) gap junction protein was demonstrated in rat adrenal glands and in primary adrenal cell cultures. The alpha 1 gap junction proteins were present in different amounts such that little or no alpha 1 antigen was detected in the zona glomerulosa (ZG), while cells of the zona fasciculata (ZF) and zona reticularis (ZR) stained intensely. There was an inverse relationship between cell division rate and gap junction number in the intact adrenal gland. We placed the cells from the most intensely staining areas (ZF/ZR) of the rat adrenal cortex into culture. These primary adrenal cells expressed alpha 1 gap junction antigen on their cell surfaces in regions of cell-cell contact. ACTH (40mU/ml) treatment resulted in an increase in gap junction expression relative to controls in primary rat adrenal cultures. These results indicate that the abundance of gap junction expression is differential in the cortical zones and can be modulated by hormonal stimulation. These observations are also thought to reflect morphological and functional differences in adrenal cortical zones.