BILIARY LIPID SECRETION DURING EARLY POSTEMBRYONIC DEVELOPMENT IN 3 FISHES OF AQUACULTURAL INTEREST - SEA-BASS, DICENTRARCHUS-LABRAX L, SEA-BREAM, SPARUS-AURATA L, AND PIKE-PERCH, STIZOSTEDION-LUCIOPERCA (L)

The mechanism of biliary lipid secretion, which is poorly documented i n high vertebrates and unknown in fish, was studied using cytochemistr y and electron microscopy during early post-embryonic development in t hree teleostean species of aquacultural interest: sea bass, Dicentrarc hus labrax L., sea bream, Sparus aurata L., and pike-perch, Stizostedi on lucioperca (L). Lipids that could be involved in biliary secretion were found in different parts of the hepatic system. VLDL-like particl es were observed in the endoplasmic reticulum and in some Golgi vesicl es of hepatocytes. In other vesicles of Golgi areas and in pericanalic ular vesicles, lipids appear as finely granular and even homogenous ma terials. These vesicles present acid phosphatase activity. Lipids are also found in the lumen of bile canaliculi, cholangioles, cystic duct, and bile vesicle. These results suggest involvement of the hepatocyte endoplasmic reticulum and Golgi apparatus in the synthesis of biliary lipids that would then be transported by vesicles and secreted in the biliary tract through exocytosis. During ontogenesis, development of the Golgi apparatus in hepatocytes leads to high production of lipid-c ontaining pericanalicular vesicles, at mouth opening. This process dec reases in pike-perch and stops in sea bass and sea bream during the fo llowing 4 to 5 days. It then resumes and increases in all three specie s. These results are in agreement with data concerning the development of biliary secretion in mammals. (C) 1997 Wiley-Liss, Inc.