Hormonal Regulation of the mRNA for Cysteine‐Rich Intestinal Protein in Rat Jejunum During Maturation

Abstract

SummaryCysteine‐rich intestinal protein (CRIP) has been implicated as an important zinc‐binding protein in the rat intestine. However, its specific role remains undefined. As an approach to the ultimate elucidation of the function of CRIP, we have explored the role of glucocorticoids and L‐thyroxine (T4) in the increase of CRIP mRNA that occurs during postnatal development. Hydrocortisone administration on day 10 elicited a precocious increase of CRIP mRNA. The response to hydrocortisone was readily detectable 12 h after injection. Lack of endogenous glucocorticoids in rat pups adrenalectomized on day 9 impeded but did not prevent the normal rise of CRIP mRNA. Furthermore, injections of dexamethasone (DEX) on days 10, 16, and 18 led to a loss of responsiveness of CRIP mRNA as the pups matured. The administration of T4 alone resulted in a small increase of CRIP mRNA, whereas when combined, T4 and DEX synergistically raised the concentration of CRIP mRNA. All of these patterns of response to hormone manipulation indicate the possibility that CRIP is a mediator of glucocorticoid action on the developing intestine. They do not appear to support the hypothesis that CRIP plays a role in zinc transport during the postnatal period. The potent effects of glucocorticoids and T4 on CRIP mRNA levels should provide useful tools for further investigations in this area.