Fasting does not increase mRNA levels of proteolytic systems in small intestinal mucosa of the rat

Fasting results in rapid and profound wasting of the small intestine, mRNA levels of genes encoding critical components of proteolytic systems were me asured in small intestinal mucosa to indirectly assess the possible role th at proteolysis plays in mediating this wasting. Male Sprague-Dawley rats (1 20 g; n = 6 per group),were either fed or fasted for 1 or 2 days. Small int estinal mucosal mass decreased by 19% and 31% after 1 and 2 days of fasting , respectively (P < 0.05). Fasting did not significantly change mRNA levels for lysosomal (cathepsin B) or ubiquitin-proteasome-dependent (ubiquitin, 14-kDa ubiquitin-conjugating-enzyme E2, and the C8 and C9 proteasome subuni ts) systems. Northern hybridizations were also performed using membranes ma de with poly A(+) mRNA instead of total RNA. mRNA levels for these proteoly tic systems and m-calpain did not significantly change with fasting. These data clearly demonstrated that fasting does nor increase expression of gene s encoding critical components of proteolytic systems in the small intestin al mucosa, suggesting that increased proteolysis cannot explain wasting of the small intestinal mucose during brief fasting in young rats. (J. Nutr. B iochem. 11: 496-499, 2000) (C) Elsevier Science Inc. 2000. All rights reser ved.