Unique characteristics of the neonatal intestinal mucosal barrier.

The purpose of this study was to compare the newborn and weanling intestinal mucosa to determine differences in: (1) the electrophysiologic characteristics of the mucosal barrier; (2) the effects of glutamine supplementation on these physiological characteristics; and (3) transmucosal bacterial passage. The Ussing chamber was used to study ileal mucosa from newborn (1 to 4 days old) and weanling (21 days old) piglets. After the seromuscularis was stripped off the bowel wall, the mucosa was mounted in the chamber and perfused with Hanks Balanced Salt Solution (HBSS) or HBSS + 20 mmol/L of glutamine. Following initial stabilization, potential difference (PD) and resistance (R) were measured at 30-minute intervals for 2 hours. Transmucosal bacterial passage was measured by quantitative cultures of the mucosal and serosal reservoirs obtained 2 hours after adding 10(8) E coli C-25 to the mucosal reservoir. Six groups of membranes were studied: (1) newborn and HBSS; (2) weanling and HBSS; (3) newborn and HBSS + glutamine; (4) weanling and HBSS + glutamine; (5) newborn - HBSS + glutamine + E coli; and (6) weanling - HBSS + glutamine + E coli. Newborn ileal mucosa had significantly lower PD and R compared with weanling at all time points. Glutamine led to a significant increase in PD in both newborn and weanling. Newborn mucosa had a significantly increased incidence of transmucosal bacterial passage (4/7) compared with weanling (0/10). These findings suggest that: (1) newborn mucosal barrier has uniquely different electrophysiologic characteristics; (2) glutamine improves the metabolic activity as measured by PD in both newborn and weanling; and (3) the newborn mucosal barrier allows increased transmucosal passage of bacteria.