HISTOLOGICAL-CHANGES INDUCED BY DIETARY PHOSPHOLIPIDS IN INTESTINE AND LIVER OF COMMON CARP (CYPRINUS-CARPIO L.) LARVAE

Histological observations were made in common carp larvae in order to understand the origin of the phospholipid (PL) requirement of fish dur ing their young stages. Larvae were fed for 6 or 8 days after start-fe eding on semi-purified diets containing peanut oil and supplemented wi th or without different PL fractions enriched in phosphatidylcholine ( PC) or phosphatidylinositol (PI). A group of larvae was also fed Artem ia nauplii, Dietary PL deficiency was associated with an accumulation of fat droplets in the enterocytes of the anterior intestine, an incre ase in height of mucosal epithelium, a reduced total liver volume and mean hepatocyte volume. In contrast, diet supplementation with PC from hen egg yolk or from soybean prevented the intestinal steatosis and r esulted in larger liver volume and larger hepatocyte volume, Larvae fe d Artemia showed the same features as larvae fed PC-enriched diets. Hy drogenated PC also prevented the intestinal steatosis but resulted in small liver and hepatocyte size. Larvae fed PI-enriched diets exhibite d intestinal steatosis, although less systematically than larvae fed P L-deficient diets, and reduced liver and hepatocyte size, Results supp ort previous opinions that PL are needed for the absorption of neutral lipids although their beneficial effect appears to be independent of their emulsifying properties. The limiting stage seems to be the synth esis and exportation of chylomicrons or very low density lipoprotein ( VLDL) by the enterocytes and not the intraluminal formation of micelle s. PC appears to have a specific role for chylomicrons and VLDL synthe sis and secretion, as in mammals. The reduced liver and hepatocyte siz e in the absence of PC could result from a decreased energy supply due to poor lipid absorption. (C) 1998 Elsevier Science B.V.