Intestinal transport of sodium, glucose and immunoglobulin in neonatal pigs. Effect of glucocorticoids.

The effect of cortisol on plasma immunoglobulin G (IgG) levels and on jejunal transport of sodium and glucose has been investigated in neonatal pigs (0-7 days of age). Five pigs were delivered vaginally (VD) at term (114-115 days gestation) and thirty-five by caesarean section (CS) 2-4 days before term (to circumvent a neonatal cortisol surge). Postnatally, twenty-seven CS pigs were injected with adrenocorticotrophic hormone (ACTH; n = 13), metyrapone (an inhibitor of adrenal 11 beta-hydroxylase activity, n = 7) or physiological saline (n = 7). Pigs were killed at birth, at 3 days, or at 6-7 days of age. Plasma concentrations of cortisol and IgG were determined and unidirectional fluxes of sodium and glucose measured across the proximal jejunum in vitro. Newborn CS pigs had significantly lower plasma cortisol but higher net fluxes of sodium and glucose than newborn VD pigs. At 3-7 days, metyrapone-treated pigs had significantly lower concentrations of cortisol and IgG in plasma and lower net fluxes of sodium and glucose than ACTH-treated pigs. Differences in net fluxes between treatment groups resulted from changes in both electrogenic and non-electrogenic sodium transport. Furthermore, sodium-glucose co-transport accounted for a major proportion of net sodium transport. High unidirectional fluxes in newborn CS pigs may be explained by the passage of large amounts of sodium through tight junctions and paracellular pathways in the prepartum period. The results indicate that cortisol stimulates net transport of sodium, glucose and immunoglobulins in the postnatal period of caesarean-delivered pigs. However, cortisol is unlikely to play a major regulatory role in the postnatal maturation of intestinal transport in normally delivered pigs.