Upregulation of nutrient transport in fetal rabbit intestine by transamniotic substrate administration.

Abstract

Intrauterine growth retardation complicates 3% to 7% of full‐term pregnancies. The developing fetal gastrointestinal tract has the ability to absorb nutrients delivered via the amniotic sac. It is not clear, however, if this nutrient delivery does in fact aid in promoting additional maturation and development of the fetal gut. Sixteen pregnant New Zealand White rabbits underwent celiotomy on gestational day 24. The bicornuate uterus was exposed, and the ovarian‐end fetuses were randomly assigned to either a control or a study group. A catheter was placed in the amniotic cavity in each side of the uterus for nutrient infusion and was secured in place. Both catheters were exteriorized; animals were partially restrained but were allowed free access to food and water. Immediately postoperatively, infusion of either a metabolizable carbohydrate (d‐galactose; experimental group) or a nonmetabolized, nontransported carbohydrate (mannitol; control group) was carried out. Six days later, each fetus was harvested. A segment of intestinal sleeve was inverted, and uptakes of radiolabeled glucose and galactose were determined in proximal, middle, and distal segments of the small intestine.No significant differences were noted in fetal body weight or fetal small intestinal length between control and experimental groups. Mucosal weight, expressed as percent of total small intestinal weight, was significantly greater only in the proximal intestinal segment in the experimental group when compared with the control group.Mucosal galactose uptake (nmol/mg of protein per minute) for each intestinal segment was determined and significant increases were noted in the experimental group, in the middle and distal segments, when compared with the control group. However, no significant differences between the two groups were noted when galactose uptake was expressed in nmol/cm per minute. Mucosal glucose uptake (nmol/mg per minute) was significantly increased in the proximal and distal segments, but not in the middle segment, of the small intestine. Again, the differences in glucose uptake between the two groups were not statistically significant when expressed as nmol/cm per minute. Nutrient uptake, calculated for the entire small intestine, was significantly greater (p <.05) in the experimental group compared with the control group.The authors concluded that the developing fetal rabbit is capable of upregulating its intestinal mucosal brush border transport in response to administration of galactose in the amniotic fluid.