Immunohistochemical identification of cells expressing steroidogenic enzymes cytochrome P450scc and P450 aromatase in taste buds of rat circumvallate papillae.

The present study demonstrated for the first time the localizations and patterns of expression of key enzymes for steroidogenesis, cytochrome P450 side-chain-cleavage (P450scc), and P450 aromatase in the taste buds of rat circumvallate papillae, using immunoblot analyses and immunohistochemistry. Immunoblot analyses showed that proteins with a molecular weight close to that of rat adrenal cytochrome P450scc and a molecular weight close to that of rat ovary cytochrome P450 aromatase were present in the rat circumvallate papillae. In immunohistochemistry, antibodies against cytochrome P450scc and P450 aromatase yielded the labelings of a subset of taste bud cells. In the double immunolabeling of P450scc and alpha-gustducin or phospholipase C beta2(PLCbeta2), which were considered as markers of a majority of type II cells, P450scc was co-expressed in a subset of alpha-gustducin or PLCbeta2, but did not co-express neural adhesion molecule (NCAM), a marker of major type III cells. Further double immunolabeled studies showed that P450 aromatase was co-expressed in a subset of alpha-gustducin or PLCbeta2, but did not co-express PGP9.5, a marker of a majority of type III cells. The selective localization of cytochrome P450scc and P450 aromatase strongly suggests that estrogen biosynthesis from cholesterol might occur in a subset of type II cells of the rat taste buds. Although the full significance of estrogen in the taste bud function is not yet understand, estrogen appears to be an important regulator of taste transduction, as is the case with ATP (Finger et al., 2005), which further supports the centrality of taste cells in the life of taste buds.