INDUCTION AND DISTRIBUTION OF CELLULAR RETINOL-BINDING PROTEIN, TYPE-2 DURING VILLUS-CRYPT DEVELOPMENT IN THE CHICK DUODENUM

Between day 18 of embryogenesis and 1 day posthatch, a rapid and remarkable (over 10-fold) increase in cellular retinol-binding protein, type two (CRBP(II)) levels occurred in the lower portion of duodenal villi of the chick. With further postnatal growth and concomitant with initiation of food intake, CRBP(II) levels increased over 2-fold in the mid-villus enterocytes. The results suggest that a first induction of CRBP(II) occurs in differentiating lower villus enterocytes during the perinatal period and is followed by marked increases in mid-villus cells. These quantitative change in the distribution and levels of CRBP(II) are probably related to the appearance of retinol in the duodenal lumen.