Development of the bile acid pool in rats from neonatal life through puberty to maturity.

The bile acid pools of developing rats were measured by gas-liquid chromatography. From shortly after birth the bile acid pools fell to a nadir on the 10th day of life (0.295 +/- 0.031 mg X g-1 body weight at 2 days to 0.144 +/- 0.012 mg X g-1 body weight at 10 days, p less than 0.001). The pool re-expanded rapidly between the 12th and 15th day. After weaning and during puberty there was a further temporary increase in pool size, during which females had larger pools than males. By adulthood the pool size had returned to the 2-day-old and weanling (15- and 18-day-old) levels, expressed per gramme body weight, and there was no longer a significant sex difference. These results show that changes in pool size are occurring at times when there are major physiological changes in the developing animal. The changes during puberty suggest hormonal control.