DIETARY-REGULATION OF ACTIVITIES AND MESSENGER-RNA LEVELS OF TRYPSIN AND AMYLASE IN SEA BASS (DICENTRARCHUS-LABRAX) LARVAE

Specific activities and mRNA levels of trypsin and amylase were studie d in sea bass larvae. From day 20 to day 30, Dicentrarchus labrax were fed two rations of one day old Artemia: satiation (LP) and one-eighth of the satiation ration (LP/8) or two isoenergetic compound diets tha t varied in protein (30 and 60%) and carbohydrate (37 and 7%) content (FP30 and FP60 respectively). Trypsin mRNA levels and specific activit ies were mainly influenced by the nature of dietary protein and the Ar temia ration. By using fish meal as protein source, dietary protein co ncentration did not affect either mRNA level nor specific activity of trypsin. These results suggested that the trypsin synthesis was not af fected at a transcriptional level by the protein ration, i.e., Artemia ration. Decrease in amylase mRNA observed from day 29 in the four die tary groups suggested that this decrease in amylase expression is gene tically programmed during sea bass larvae development. Nevertheless, t he composition and the quantity of the diet influenced the amylase spe cific activities revealing primarily translational regulation of amyla se. This study shows for the first time that the molecular mechanisms which control the dietary adaptation of trypsin and amylase an indepen dently regulated, age-dependent and influenced by the composition and the quantity of the diet.