METALLOTHIONEIN-IIA PROMOTER INDUCTION ALTERS RAT INTESTINAL FATTY-ACID-BINDING PROTEIN EXPRESSION, FATTY-ACID UPTAKE, AND LIPID-METABOLISMIN TRANSFECTED L-CELLS

Mouse L-cell fibroblasts, transfected with the cDNA encoding for rat i ntestinal fatty acid-binding protein (I-FABP) under the control of the human metallothionein-IIA promoter, were tested for their protein ind ucibility by the heavy metals cadmium (Cd2+) and zinc (Zn2+), I-FABP l evels were quantitated by Western immunoblotting, Expression of I-FABP in all transfected cell lines tested was induced several-fold by opti mized levels of Cd2+ and Zn2+, Induction conditions had no effect on c ell growth rates or cell densities for any of the cell lines, Inductio n of high I-FABP-expressing cells (H141) decreased the initial rate an d extent of uptake of cis-parinaric acid, a nonmetabolizable fatty aci d, and of [H-3]oleic acid, an esterifiable fatty acid, These effects o f induction were specific for I-FABP-expressing cells since they were not observed in control cells or cells expressing a high level of live r (L-) FABP, Induction of H141 cells also significantly altered the es terification and distribution of exogenous [H-3]oleic acid, especially among triglycerides and phosphatidylcholine, but less so among other glycerophospholipids, cholesteryl esters, and phosphatidylethanolamine . Induction of H141 cells normalized [H-3]oleic acid esterification in to cholesteryl esters, phosphatidylcholine, total neutral lipids, and total phospholipids such that they no longer differed from control lev els, In contrast, induction did not normalize [H-3]oleic acid esterifi cation into triacylglycerols and phosphatidylethanolamine ID control l evels in H141 cells; both remained significantly increased over contro l cells, Therefore, promoter induction levels of Cd2+ and Zn2+ enhance d I-FABP expression in H141 cells, thereby modulating both fatty acid uptake and intracellular esterification into neutral and phospholipids . (C) 1997 Academic Press.