EFFECT OF EARLY DIETARY DEFICIENCY IN POLYUNSATURATED FATTY-ACIDS ON 2 LECTIN-BINDING SITES IN THE SMALL-INTESTINE OF POSTWEANLING RATS

This study was designed to determine whether dietary lipids influence the development of intestinal cell glycosylation, in relationship to diet-induced changes in phospholipid fatty acid composition. The ability of two different lectins, wheat germ agglutinin (WGA) and Maackia amurensis agglutinin (MAA), to combine specifically with particular carbohydrate residues was used to investigate the surface characteristics of epithelial cells of rats fed different dietary lipids from birth to 6 weeks of age. Diets contained 5% (weight) peanut oil (PO), rich in n-6 fatty acids; salmon oil (SO), rich in n-3 fatty acids; hydrogenated palm oil (HPO), deficient in both n-6 and n-3 fatty acids or a PO and rapeseed oil (RO) mixture (PRO), the control diet. Pieces of jejunal and ileal villi were excised from postweanling rats and prepared for lectin histochemical study. Concurrently, epithelial cells were removed from jejunal and ileal segments for determining their phospholipid fatty acid compositions. Polyunsaturated fatty acid (PUFA) deficiency was evidenced in the HPO group by the appearance of eicosatrienoic acid (20:3n-9) in both jejunal and ileal phospholipids, which paralleled the decrease in arachidonic acid content. Accretion of 18:1n-9 and 20:30-9 in cell phospholipids of group HPO was not sufficient to match the unsaturation level in rats fed nonhydrogenated vegetable oils (PRO, PO) or fish oil (SO). The lectin histochemical study showed that WGA strongly labelled the brush border membrane microvilli whereas binding of MAA was specific to goblet cells and mucus. Regardless of the type of diet, WGA binding was weaker in the ileum than in the jejunum. In comparison to all other groups, WGA-labelling of villi was less intense in the jejunum and disappeared almost completely in the ileum of HPO-fed rats. Although SO- and PO-fed rats had, respectively, very low and high ratios of n-6 to n-3 in their intestinal phospholipids, binding of WGA in both groups was not markedly different from that in the control (PRO). MAA-labelling was very intense in jejunal and ileal villi of n-3-fed (SO) rats, whereas it was strongly attenuated in the n-3- and n-6 deficient (HPO) group. These results suggest that intestinal glycosyltransferase activities involved in cell differentiation were altered relative to the overall unsaturation index of dietary fatty acids. Alterations of epithelial glycosylation mainly resulted from a drop in total n-6 and n-3 fatty acids, although it may be speculated that there is a specific effect of n-3 fatty acids.