The expression of retinoic acid receptor α, β, and Γ mRNA was examined in developing rat livers and rat hepatoma-derived cell lines H-4-II-E, McA-RH 7777, and 8994 that represent different hepatocyte phenotypes. Northern blot hybridization demonstrated that all three receptor mRNAs were expressed in the fetal livers of different gestational ages, and the levels of expression increased significantly 3 to 4 weeks after birth. In the hepatoma cell lines, the expression pattern of retinoic acid receptor α and Γ mRNA did not correlate with the phenotype. In contrast, retinoic acid receptor β mRNA was only detected in the adult phenotypic H-4-II-E cells but not in McA-RH 7777 and 8994 cells, which represent embryonic and fetal hepatocyte phenotypes, respectively. The levels of retinoic acid receptor β mRNA in hepatoma cell lines were lower than adult rat liver. These data suggest that the increased expression of retinoic acid receptor β gene is associated with differentiation or maturation of rat hepatocytes. The effect of retinoic acid on retinoic acid receptor gene expression was also studied in hepatoma cells. Retinoic acid did not regulate retinoic acid receptor gene expression in McA- RH 7777 and 8994 cells, and the retinoic acid receptor β gene remained inactivated in these cells. However, Southern blot hybridization indicated that the gross structure of retinoic acid receptor β gene was not altered during malignant transformation. In H-4-II-E cells, retinoic acid increased the expression of retinoic acid receptor β and Γ gene. Because of the similarity between H-4-II-E cells and normal adult hepatocytes, this type of autoregulation may be a mechanism by which retinoic acid regulates its own effect in vivo.
|Original language||English (US)|
|Number of pages||6|
|State||Published - 1992|
ASJC Scopus subject areas
- Pathology and Forensic Medicine