Abstract
The effect of breast milk and 3α, 20β-pregnanediol on the conjugation of bilirubin and o-aminophenol by rat liver was compared. Breast milk inhibited glucuronyl transferase, whereas 3α, 20β-pregnanediol inhibited the secretion of bilirubin glucuronide from rat liver slices. In the inhibitory breast milk examined the steroid was probably not the sole inhibitory factor.