EXPRESSION OF MONOCARBOXYLATE TRANSPORTER MCT1 BY BRAIN ENDOTHELIUM AND GLIA IN ADULT AND SUCKLING RATS

A polyclonal affinity-purified antibody to the carboxyl-terminal end o f the rat monocarboxylate transporter 1 (MCT1) was generated in chicke ns and used in immunocytochemical studies of brain tissue sections fro m adult and suckling rats. The antibody identified a 48-kDa band on im munoblots and stained tissue sections of heart, cecum, kidney, and ske letal muscle, consistent with the reported molecular mass and cellular expression for this transporter. In tissue sections from adult brains , the antibody labeled brain microvessel endothelial cells, ependymocy tes, glial-limiting membranes, and neuropil. In brain sections from 3- to 14-day-old rats, microvessels were much more strongly labeled and neuropil was weakly labeled compared with sections from adults. Immuno electron microscopy indicated that labeling was present on both lumina l and abluminal endothelial cell plasma membranes. These results sugge st that MCT1 may play an important role in the passage of lactate and other monocarboxylates across the blood-brain barrier and that sucklin g rats may be especially dependent on this transporter to supply energ y substrates to the brain.