Substrate-induced acceleration of lactase synthesis in fetal rat intestine.

Twenty milligrams of lactose were injected into the amniotic sacs of fetuses in one uterine horn and 20 mg glucose were injected into the amniotic sacs of fetuses in the opposite uterine horn of six rats on days 17-19 of pregnancy. Two or 3 days later the pregnant animals were killed and segments of jejunum obtained from their fetuses were homogenized in water. Assays for lactase and protein determinations were performed on these homogenates. Lactase values were significantly higher in the lactose-injected group than in fetuses receiving glucose (Table 2), P less than 0.0005. Thus, fetal intestinal lactase activity can be increased by exposure to the substrate lactose during late fetal life.