Rk. Buddington et C. Malo, INTESTINAL BRUSH-BORDER MEMBRANE ENZYME-ACTIVITIES AND TRANSPORT FUNCTIONS DURING PRENATAL DEVELOPMENT OF PIGS, Journal of pediatric gastroenterology and nutrition, 23(1), 1996, pp. 51-64
Enzyme activities and rates of leucine and glucose uptake were measure
d using brush-border membrane vesicles prepared from the small intesti
ne of 7- 8-, 10-, and 12-week fetal (43, 49, 61, and 74% of gestation)
and unsuckled, neonatal pigs. Lactase was detected in 7-week fetuses,
with a large increase in activity between 10 weeks of gestation and b
irth. gamma-Glutamyltranspeptidase activity was stable throughout gest
ation, whereas sucrase activity was not detected. Active L-leucine upt
ake was already present at 7 weeks of gestation, with an increasing di
stal-to-proximal gradient observed at birth. D-glucose uptake was low
at 7 weeks, but by 8 weeks it exhibited a typical overshoot phenomenon
and established a decreasing proximal-to-distal gradient by 12 weeks.
D-glucose uptake at all ages was directly related to incubation tempe
rature, but less so for 7- and 10-week fetuses. By 12 weeks strict Na-dependency of D-glucose uptake was observed along the entire length o
f the small intestine. Kinetic analysis of Na+-D-glucose cotransport s
howed a shift from the presence of both high- and low-affinity systems
at 8 weeks of gestation to a single high-affinity Michaelian componen
t at birth. In light of similarities with human fetuses, the pig may b
e a valuable model for studying development of intestinal transport du
ring gestation, particularly during the final trimester, when availabi
lity of human tissue is limited.