SUCKLING INDUCES RAPID INTESTINAL GROWTH AND CHANGES IN BRUSH-BORDER DIGESTIVE FUNCTIONS OF NEWBORN PIGS

The interplay between suckling, intestinal growth and brush-border mem brane functions is critical during the perinatal period. The present s tudy investigates changes in intestinal dimensions, activities of four brush border membrane hydrolases (lactase, sucrase, maltase and amino oligopeptidase) and rates of sugar and amino acid uptake by intact tis sues and brush border membrane vesicles during the first 24 h of suckl ing. Total intestinal weight, mucosal weight and protein content incre ased 58%, 80% and 126% (P < 0.05) during the first 6 h of suckling; le ngth and surface area did not increase. Total mucosal DNA content was 4.6-fold higher at 24 h after birth, with the rate of increase differi ng among intestinal regions. Hydrolytic capacities of the entire small intestine increased, more so for homogenates than for brush border me mbrane vesicles, and more for lactase relative to the other hydrolases studied. Rates of nutrient transport declined, especially for brush b order membrane vesicles, for proximal and mid-intestine relative to di stal intestine, and for glucose relative to galactose and amino acids. We conclude that 1) changes in brush border membrane digestive functi ons coincide with rapid intestinal growth, with postnatal patterns var ying among hydrolases, transporters and regions; 2) insertion into the brush border membrane, not synthesis, limits the postnatal increase o f hydrolase activity; and 3) despite declines in specific activity, hy drolytic and glucose transport capacities of the entire intestine rema ined stable or increased, and exceeded estimated dietary loads because of intestinal growth.