Short- and long-term regulation of rat carotid body gap junctions by cAMP. Identification of connexin43, a gap junction subunit.

Intact and cultured carotid bodies (CBs) of the rat were used in this study. Applications of membrane-permeant db-cAMP to cultured carotid bodies increased electric coupling between most glomus cells (increasing junctional conductance) probably by opening preformed intercellular channels. This a short-term effect of the nucleotide, increasing gating between glomus cells. When cultures and intact carotid bodies were treated with membrane-permeant 8Br-cAMP for 3 h or more (to increase cytosolic cAMP), there was enhanced gap junction formation and better dye spread between carotid body cells. Connexin43 (CX43) was identified by immunocytochemical methods as forming part of the intercellular channels between carotid body cells, and the expression of Cx43 increased by cAMP. This is a long-term effect, inducing the formation of gap junctions. Thus, cAMP had short and long-term effects on the intercellular junctions of the carotid body. Long-term formation of gap junctions may be important in modulating carotid body functions during stimulation by chronic hypoxia.