Biliary lipid secretion during early post-embryonic development in three fishes of aquacultural interest: Sea bass, Dicentrarchus labrax L., sea bream, Sparus aurata L., and pike-perch, Stizostedion lucioperca (L)

Abstract

The mechanism of biliary lipid secretion, which is poorly documented in high vertebrates and unknown in fish, was studied using cytochemistry and electron microscopy during early post-embryonic development in three teleostean species of aquacultural interest: sea bass, Dicentrarchus labrax L., sea bream, Sparus aurata L., and pike-perch, Stizostedion luciopera (L). Lipids that could be involved in biliary secretion were found in different parts of the hepatic system. VLDL-like particles were observed in the endoplasmic reticulum and in some Golgi vesicles of hepatocytes. In other vesicles of Golgi areas and in pericanalicular vesicles, lipids appear as finely granular and even homogenous materials. 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-containing pericanalicular vesicles, at mouth opening. This process decreases in pike-perch and stops in sea bass and sea bream during the following 4 to 5 days. It then resumes and increases in all three species. These results are in agreement with data concerning the development of biliary secretion in mammals. J. Exp. Zool. 277:365–370, 1997. © 1997 Wiley-Liss, Inc.