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Meprin is a zinc-metalloendopeptidase expressed in intestinal epithelial cells. In rat jejunum collected from postnatal day 4 (P4) through P25 meprins alpha mRNA exhibited uniform levels for the first three postnatal weeks and then declined, whereas meprin beta mRNA showed a biphasic pattern with high levels in the first postnatal week followed by low levels from P7 through P19 and then a marked rise at P22 and P25. Dexamethasone treatment beginning at P10 had no significant effect on levels of meprins a mRNA, whereas this treatment caused a precocious increase in expression of meprin beta mRNA. These divergent patterns of expression of meprins alpha and beta mRNA suggest distinct roles for the two subunits during the suckling and weaning phases of rodent intestinal development.

A partial rat trehalase cDNA has been cloned and used to examine trehalase mRNA expression. Northern blotting with total RNA from 11 adult rat tissues showed a trehalase transcript only in small intestine, where it was abundant in proximal regions but declined steeply toward the ileum. During development, trehalase mRNA was not detectable in jejunum until postnatal day 19 and then increased markedly through day 25. Modest levels in trehalase mRNA were induced precociously by administration of dexamethasone, with increasing responsiveness evident between the first and second postnatal weeks. In contrast, analysis of sucrase-isomaltase mRNA on the same blots showed maximal induction at both ages. In adrenalectomized animals, the ontogenic increase of trehalase mRNA began as usual but proceeded more slowly than in control animals. Overall, trehalase mRNA expression in the rat displayed both similarities and differences compared with rabbit. Moreover, the differences revealed in glucocorticoid responsiveness of trehalase mRNA and sucrase-isomaltase mRNA suggest that the actions of these hormones on the developing intestine may be more complex than previously recognized.