Cellular localization of type 5 and type 6 ACs in collecting duct and regulation of cAMP synthesis

Abstract

The cellular distribution of Ca2+-inhibitable adenylyl cyclase (AC) type 5 and type 6 mRNAs in rat outer medullary collecting duct (OMCD) was performed by in situ hybridization. Kidney sections were also stained with specific antibodies against either collecting duct intercalated cells or principal cells. The localization of type 5 AC in H+-ATPase-, but not aquaporin-3-, positive cells demonstrated that type 5 AC mRNA is expressed only in intercalated cells. In contrast, type 6 AC mRNA was observed in both intercalated and principal cells. In microdissected OMCDs, the simultaneous superfusion of carbachol and PGE2 elicited an additive increase in the intracellular Ca2+ concentration, suggesting that the Ca2+-dependent regulation of these agents occurs in different cell types. Glucagon-dependent cAMP synthesis was inhibited by both a pertussis toxin-sensitive PGE2 pathway (63.7 ± 4.6% inhibition, n = 5) and a Ca2+-dependent carbachol pathway (48.6 ± 3.3%, n = 5). The simultaneous addition of both agents induced a cumulative inhibition of glucagon-dependent cAMP synthesis (78.2 ± 3.3%, n = 5). The results demonstrate a distinct cellular localization of type 5 and type 6 AC mRNAs in OMCD and the functional expression of these Ca2+-inhibitable enzymes in intercalated cells.