RESEARCH OF AN IN-VITRO MODEL TO STUDY THE EXPRESSION OF FATTY-ACID-BINDING PROTEINS IN THE SMALL-INTESTINE

In order to find an in vitro model for studying the regulation of the biosynthesis of the cytoplasmic Fatty Acid-Binding Proteins (FABPc) ex pressed in the small intestine, Intestinal- and Liver- (I- and L-) FAB Pc expressions were tested by Northern blotting in 8 normal or cancero us intestinal cell lines from man, mouse and rat and in organ culture of mouse jejunal explants. Neither 1- nor L-FABPc mRNA was detected in any cell strains tested except in the highly differentiated human ent erocyte-like intestinal cell line Caco-2. In this line, Northern blot analysis revealed a single messenger of about 0.7 kb corresponding to the L-FABPc. A two-fold increase in mRNA L-FABPc occurred in different iated Caco-2 cells treated for 7 days with 0.05 mM bezafibrate, a pero xisome-proliferating hypolipidemic drug. The lack of I-FABPc messenger s in this strain led us to seek another in vitro model. I- and L-FABPc messengers were found using an organ culture of mouse jejunal explant s. A clear rise in I- and, especially, L-FABPc mRNA levels occurred 6 and 24 hr after the addition of 0.05 mM bezafibrate in the culture med ium. Our results demonstrate, to our knowledge for the first time, tha t: 1) organ culture of intestinal explants provides a useful model for studying in vitro the simultaneous regulation of 1- and L-FABPc expre ssions, 2) biosynthesis of L-FABPc may be explored in vitro using the Caco-2 cell line, 3) fibrate peroxisome-proliferators exert a direct e ffect on I- and L-FABPc expression in the small intestine, 4) L-FABPc expression seems to be more sensitive to fibrate action than is I-FABP c expression.