Cellular retinol binding protein during postanal development of the rat small intestine.

Levels of the cellular retinol-binding protein (CRBP) were measured in extracts of rat small intestine from 1 day before birth to day 21 postnatally. Changes in the amount of CRBP per cell were observed. The highest levels were observed in the 1-day-old rat. The amount of CRBP gradually declined until the animals reached the age of 21 days. Thereafter only a slight decline was observed. The postnatal development of CRBP was similar in the jejunum and the ileum, with the jejunum always showing higher levels. However, CRBP was detectable in the jejunum but not in the ileum of adult rats.