Retinol binding protein (RBP) is a carrier molecule for retinol in plasma. Zn deficiency leads to a reduction in circulating levels of RBP-retinol and an elevation in liver retinol. Although postulated to reflect impaired mobilization the molecular mechanism underlying this process is unknown. In the current work, we have examined the effects of intracellular Zn concentration on RBP mRNA and protein levels in human hepatoma (Hep-G2) cells. Cells were grown in non-dialyzed control media (7.5% FBS, 4 μM Zn) or in dialyzed media containing 0.5, 15, or 50 μM Zn. After 24 h in culture, RBP mRNA levels were similar under all conditions. However, intracellular RBP protein levels were markedly elevated in both 0.5 and 15 μM groups. After 48 and 72 h of culture, relative to controls, cells incubated in 0.5 μM Zn exhibited a 5 and 8-fold increase in RBP mRNA, while cells in 15 μM Zn showed only a 3-fold increase. Intracellular RBP protein levels were also high in these two groups. Cells grown in 50 μM Zn were characterized by control levels of RBP mRNA and protein. Given that RBP gene expression is inducible by cAMP, we suggest that the above effects are mediated in part by Zn deficiency- induced changes in cAMP metabolism.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology