Connexin 43 ontogeny in fetal sheep adrenal glands.

We examined fetal sheep adrenal glands from 99 to 130 days of gestational age (dGA) to see how connexin 43 (Cx43), the major if not the only adult adrenal gap junction protein, changes expression as the adrenal cortex emerges from the well-documented refractory period to participate in labor and delivery. Immunocytochemical technique and Western blot were used to examine changes in the quantity and quality of Cx43. In addition, adrenal glands of ACTH infused fetuses or of fetuses from dexamethasone injected ewes underwent image analysis quantification after Cx43 immunostaining. Finally, fetal adrenal glands, from fetuses splanchnic nerve sectioned (SPLX) at 125 dGA, were examined for the pattern of Cx43 immunostaining at 131 days of gestation. From 100 to 130 dGA, the amount of Cx43 in cells of the adrenal cortex increased steadily while the pattern of immunoreactivity changed from predominantly cytoplasmic to membrane bound. At 100-103 dGA, ACTH infusion increased the size of the cortex, but decreased the expression of Cx43 per unit area while dexamethasone had no effect on either parameter. Lastly, the expression of Cx43 as a membrane bound protein was not delayed or reversed by SPLX. We conclude that the described changes in Cx43 are most intriguing given their temporal relationship to the described preparturient increases in ACTH and cortisol in peripheral fetal plasma as term approaches and deserve further investigation.