Probable Basis of Altered BBB Nutrient Transport in the Offspring of Severely Hypothyroid Dams.

Recently we observed increased transport of nutrients across the blood-brain barrier (BBB) in the offspring born to mothers fed a potent antithyroid compound, 6-n-propyl-2-thiouracil (PTU) during gestation and lactation. The probable basis of this altered BBB nutrient transport in these pups has now been assessed by determining the kinetics of the transport of 2-deoxy-D-glucose across the BBB in situ, the fluidity of the isolated brain microvessel plasma membranes and their fatty acid profile. The maximal transport capacity (Tmax app) of the BBB transport system was markedly increased in the pups of PTU fed dams compared to controls. The fluidity of the brain microvessel endothelial cell plasma membrane (BMVPM) was increased significantly (P < 0.05) and this appeared to be due to an increase in unsaturation index (P < 0.001)/polyunsaturated fatty acid content of BMVPMs (P < 0.005). The results suggest that the increased BBB nutrient transport in the pups of severely hypothyroid dams could be due to changes in membrane microenvironment, altering the kinetics of BBB transport system and/or exposure of latent transporters.