Differential Permeability of the Rabbit Placenta to Various Sugars

¹ From the Department of Anatomy, Washington University School of Medicine, St. Louis, Missouri

The permeability of the rabbit placenta at term has been studied by following maternal and fetal blood sugar curves during a controlled intravenous infusion of the following sugars: disaccharides (sucrose, lactose, maltose); hexoses (glucose, mannose, galactose, sorbose, fructose); pentoses (arabinose, xylose, ketoxylose) and the trisaccharides dihydroxyacetone and glyceraldehyde. The disaccharides were almost completely blocked by the placenta. Among the hexoses, and possibly among the pentoses, there was a clear differential permeability on the part of the placenta to the aldo-sugars on the one hand and the keto-sugars on the other. Results with the trisaccharides were inconclusive. The results were held to furnish added proof for the complex character of the placental transfer mechanism for sugars. No evidence was put forward for the possible mechanism involved.