The biochemical and histochemical demonstration of lactase induction in fetal rat intestine by intra-amniotic injection of lactose.

A single dose of 20 mg beta-D-lactose injected into the amniotic sac of rats on day 17 of pregnancy induced an increase in lactase activity in fetal jejunum. This effect was first noted two days after injection and lasted for at least two additional days. Histoenzymatic investigation indicated that this enzyme was located on the surface of the absorptive cells lining the villi and thus corresponds to the "dietary" form of beta-galactosidase. A much smaller increase, based presumably on progressive increase in fetal size (age) was found in control fetuses which had received glucose or no injections. Peak lactase values in fetuses receiving lactose were substantially higher than peak values in control fetuses. In both lactose-injected and non-injected rats which were allowed to deliver, there was a sharp drop in lactase values coincident with birth.