Developmental regulation of rat intrinsic factor mRNA.

Using a full-length rat intrinsic factor (IF) cDNA clone, we have examined gene expression of IF in selected tissues from the adult rat and during postnatal development in the rat stomach. IF mRNA was expressed only in the rat stomach, and in situ hybridization revealed that the expression was limited to the chief cells at the base of the oxyntic glands. IF mRNA concentration in the stomach increased with postnatal age and reached a peak at the 30th day. Postnatally the amount of IF mRNA hybridized increased in both individual cells and in total number of cells. Administration of cortisol to, or adrenalectomy of, rats between 5 and 12 days of age resulted in increase or decrease of IF mRNA levels, respectively. Other hormones tested (pentagastrin, thyroxine, and triiodothyronine) had no significant effect. During the suckling period, IF bound well to the ileal receptor, despite lower than adult levels of activity and different glycosylation, as assessed by binding to concanavalin A-Sepharose beads. These results show that developmental expression of IF activity in rat is closely related to the expression of its mRNA and that corticosteroids play an important role in such an expression.