THE EFFECT OF FASTING AND REFEEDING WITH SPIRULINA ON ENDROCRINE CELLS IN THE GASTROINTESTINAL TRACT OF ZEBRAFISH (DANIO RERIO)

Several studies on the gastrointestinal tract have documented that certain experimental procedures can act on morphological integrity, metabolism, enzymatic patterns regulation, gastrointestinal hormones and peptides transport . Danio rerio (Hamilton, 1822) zebrafish, vertebrate model used in scientific research, has been also proposed for fish nutrition studies. PepT-1 is an oligopeptide transporter responsible for absorbing di- and tri-peptides through a brush border membrane of intestinal mucosa. Cholecystokinin (CCK-8), satiety hormone secreted from endocrine cells of the gastrointestinal tract, enhanced digestion by triggering the release of pancreatic enzymes, gallbladder contraction and inhibiting gastric emptying. The aim of this study was to determine the effect of short-term food deprivation and refeeding in adult zebrafish on the gastrointestinal expression of PepT-1 and CCK-8, in order to elucidate a potential mechanism driving compensatory growth. Samplings were repeated following 2 and 5 days of fasting and 2 and 5 days of refeeding with commercial Sera Spirulina tabs, in which the major constituent is Spirulina sp. which brings 50.2% in protein. The morphological analysis and immunohistochemical determination of PepT-1 and CCK-8 by Western blot were carried out. The intestinal tract from control specimens, exhibites the simple architecture of digestive tract. Fasting 2 and 5 days caused morphostructural changes in folds and constriction of the intestinal lumen. Western blot analysis revealed a reduction in PepT-1 levels after fasting and an increase after refeeding, reaching very high levels after 5 days, compared to the control. The levels of CCK-8 decreased after food deprivation, while increased gradually after refeeding. The significant increase in expression of PepT1 in refeeding fish, following fasting, suggests a physiological mechanism contributing to compensatory growth for enhanced absorption efficiency and might influence CCK-8 secretion.