Hormone induced expression of brush border lactase in suckling rat intestine

Abstract

The postnatal development of intestine is associated with a decline in brush border lactase activity in rodents. This is similar to adulthood hypolactasia, a phenomenon prevalent in humans worldwide. In the present study, the effect of luminal proteases from adult rat intestine was studied in vitro on intestinal lactase activity in saline control, thyroxine, insulin and cortisone treated rat pups. Lactase levels were determined by enzyme analysis and Western blotting. mRNA levels encoding lactase were determined by Northern blotting. Administration of thyroxine for 4 days reduced (P<0.05) lactase activity, but insulin treatment had no effect in 8-day-old rat intestine. However, cortisone administration augmented (P<0.01) lactase activity, under these conditions. Western blot analysis showed decreased lactase signal corresponding to 220-kDa protein band in thyroxine treated animals. However, the intensity of lactase signal was high in cortisone treated animals compared to controls. mRNA levels encoding lactase showed a 6.8-kb mRNA transcript in saline and hormone treated rats. mRNA levels encoding lactase were increased in cortisone treated animals but were reduced in thyroxine injected pups compared to controls. Microvillus membranes from saline (P<0.01) and thyroxine (P<0.05) or insulin (P<0.01) treated rats upon incubation with luminal wash from adult rat intestine showed a significant decline in lactase activity. These findings suggest that thyroxine, insulin or cortisone induced changes in lactase expression in suckling rat intestine make it susceptible to luminal proteases, which may in part be responsible for observed maturational decline in lactase activity in adult rat intestine.

Glycoconjugate histochemistry in the small and large intestine of normal and Solanum glaucophyllum-intoxicated rabbits

“…The molecular pathways that trigger or regulate the glycosylation process of the intestine are not still completely defined. The regulation of the morphological and functional maturation of the mammalian small intestine is under the control of multiple hormonal and nutritional factors during postnatal life (Dauca et al, 1990;Jaswal et al, 1990;Biol et al, 1998;Biol-N'garagba and Louisot, 2003;Chaudhry et al, 2008). Among the hormonal factors, glucocorticoids modulate the gene transcription of glycosyltransferases, such as fucosyltransferases.…”

“…Thus, these hormones trigger precocious changes in the sialylation, galactosylation and fucosylation processes of the intestinal epithelium during suckling (Biol-N'garagba and Louisot, 2003). Thyroid hormones, other hormones with intracellular receptors, are also involved as regulatory factors (Mahmood and Torres-Pinedo, 1985;Chaudhry et al, 2008). In addition, undernutrition in suckling rats negatively impact on the carbohydrate composition on enterocytes glycocalix, but the administration of cortisone and insulin revert the glycosylation pattern acquired under that state (Jaswal et al, 1990).…”