Maternal-fetal exchange during protein malnutrition in the rat. Placental transfer of glucose and a nonmetabolizable glucose analog.

Maternal-fetal transfer of glucose and methyl alpha-D-glucopyranoside (AMG) was studied in rats fed either a 6% or a 27% casein diet. On day 21 of pregnancy 3H-labeled glucose and 14C labeled AMG were injected into the maternal circulation of both groups of dams and concentration of tritium and 14C in maternal plasma, placentas and fetuses were determined 10 and 20 minutes later respectively. In malnourished rats both substances tended to be slightly, although non-significantly, increased in maternal plasma and were significantly decreased in placentas and fetuses. This lower concentration in fetal tissues reflected a marked reduction in the amount of glucose and AMG transported into the fetuses per g of placental tissue per minute. The proportionality of the changes found for both substances suggests that their reduced rate of transfer may be due to similar mechanisms.