L. Ribeiro, J.L. Zambonino Infante, C. Cahu, M.T. Dinis
The variation of digestive enzymes were studied in sole larvae from first feeding until 1 month of life. Larvae were fed with rotifer from day 3 to day 5 after hatching (day 1) followed by Artemia until the end of the experiment. Whole body homogenates were used for enzymatic determination in larvae younger than 22 days. Older larvae were dissected on a glass maintained at 0 C, in order to obtain the pancreatic and intestinal segment. Brush border membranes of enterocytes were purified from intestinal segment.
Between day 4 and 19, the specific activity of trypsin increased during the first days, reaching the highest value on day 10, after what a decrease was observed until the end of the period studied. This decrease in specific activity was mainly due to the important increase in body protein rather than to a decrease in enzymatic activity, moreover, this variation in enzymatic specific activity is characteristic of developing animals.
Amylase and leucine-alanine-aminopeptidase (leu-ala), exhibited a similar pattern of variation of specific activity along this period. Specially, leu-ala decreased sharply from day 7 to 10, then maintained a constant level until the end of this period. This variation in specific activity reflects the important role of cytosolic enzymes during early stages of larvae.
In intestinal brush border membranes of dissected larvae, a strong increase in alkaline phosphatase specific activity was observed from day 22 until day 28. The development of enzymatic activities in brush border membranes suggested that intestinal maturation was initiated as early as day 22 in sole larvae.
(Universidade do Algarve - UCTRA, Campus de Gambelas, 8000 Faro, Portugal)