Enterocyte digestive enzyme activity along the crypt-villus and longitudinal axes in the neonatal pig small intestine

Our objective was to examine the distribution of enterocyte digestive enzym e activity along the crypt-villus and longitudinal axes of the small intest ine in formula-fed neonatal pigs between the ages of 14 and 18 d. The diste nded intestinal sac method was used to isolate 12 sequential fractions (F1 through F12) of epithelial cells. Enterocyte migration rate was measured in the proximal and distal intestine using in vivo bromodeoxyuridine labeling . Specific activities of representative villus cell marker enzymes of alkal ine phosphatase, aminopeptidase N, sucrase, and lactase increased 6- to 17- fold from F12 (crypt cells) to F1 (villus cells), whereas the crypt cell ma rker [H-3]thymidine incorporation increased 8- to 18-fold from F1 (villus c ells) to F12 (crypt cells). Enterocyte migration rate was similar (3.2 vs 3 .0 mum/h), whereas the villus height (547.4 vs 908.5 mum) and enterocyte li fe span (4.7 vs 10.2 d) were markedly lower (P < 0.05) in the proximal than in the distal segments, respectively. In general, the specific activities of all enzymes were lowest in the crypt fractions (F9 through F12) but incr eased markedly (ranging from 8- to 17-fold) from F12 to F1. The activity of aminopeptidase N was higher and that of sucrase was lower in the distal th an in the proximal segment. The activities of the remaining enzymes were si milar in the proximal and the distal segments. Our results suggest that the enterocyte life span in the distal small intestine is approximately twice as long as in the proximal small intestine. However, despite the difference in life span, the patterns of enzyme activities along the crypt-villus axi s were generally similar in the proximal and the distal regions.