mRNA expression of
pancreatic enzyme precursors and estimation of protein digestibility in
first feeding larvae of the Japanese flounder, Paralichthys olivaceus
A.S. Srivastava, T. Kurokawa, T. Suzuki-2002
Comparative Biochemistry and Physiology --Part A:
Molecular and Integrative Physiology, 132(3): 629-635
Abstract:
An understanding of digestibility in marine fish
larvae is required to formulate a diet to replace zooplankton. Using
flounder, this study was aimed at determining which digestive enzymes are
synthesized in the larval pancreas, and how the proteins are cleaved in the
digestive canal. Whole mount in situ hybridization indicated that the mRNA
of all digestive enzyme precursors examined, including trypsin,
chymotrypsin, elastase, carboxypeptidase A and B, and lipase, was expressed
in the pancreas of first feeding larvae at 3 days post-fertilization. In the
larvae before differentiation of the stomach, protein digestion in the
digestive canal mainly depends on pancreatic proteases. So, to evaluate
protein digestibility in the larval digestive canal, the digestion of
proteins by pancreatic extract was monitored by gel electrophoresis. It was
indicated that thyroglobulin, albumin and lactate dehydrogenase were rapidly
cleaved to polypeptide fragments, but ferritin and catalase exerted
resistance to proteolysis, suggesting that digestibility in the larval
digestive canal differs depending on protein species.
(Metabolism Section, National Research Institute of
Aquaculture, Fisheries Research Agency, Nansei, Mie 516-0193, Japan, Tel.:
+81-5996-6-1830; fax: +81-5996-6-1962, e-mail of T. Suzuki: suzukitr@fra.affrc.go.jp)