RETINYL ESTER STORAGE IS ALTERED IN LIVER STELLATE CELLS AND IN HL60 CELLS TRANSFECTED WITH CELLULAR RETINOL-BINDING PROTEIN TYPE-I

It is suggested that cellular retinol-binding proteins are important f or intracellular metabolism of retinol. Retinol bound to cellular reti nol-binding proteins may be esterified with long chain fatty acids by the enzyme lecithin: retinol acyltransferase Or may be oxidized to ret inoic acid metabolites used in the mechanism of action of vitamin A. T he aim of this present report was to determine whether altered levels of cellular retinol-binding protein type I influenced retinol storage and activation. Two different cell types have been examined after tran sfection with vectors producing sense or antisense mRNA for cellular r etinol-binding protein type 1. When HL60 cells were transfected with t he expression vector for sense cellular retinol-binding protein type I high amounts of cellular retinol-binding protein type T mRNA and prot ein were produced. We observed that HL60 cells esterified less retinol than control cells without cellular retinol-binding protein type I. C ellular retinol-binding protein type I had, however, no effects on the proliferation or differentiation of HL60 cells by retinoids. Liver st ellate cells transfected with the vector for sense cellular retinol-bi nding protein type I esterified more retinol than cells transfected wi th the expression vector for antisense cellular retinol-binding protei n type I, while retinol esterification in control cells was intermedia te. In conclusion, our data show that cellular retinol-binding protein type I influences retinol esterification both in liver stellate cells and in HL60 cells. (C) 1997 Elsevier Science Ltd.