Lactate transport in rat adipocytes: identification of monocarboxylate transporter 1 (MCT1) and its modulation during streptozotocin-induced diabetes

We have characterised L-lactate transport in rat adipocytes and determined whether these cells express a carrier belonging to the monocarboxylate tran sporter family. L-Lactate was taken up by adipocytes in a time-dependent, n on-saturable manner and was inhibited (by similar to 90%) by alpha-cyano-4- hydroxycinnamate, Lactate transport was stimulated by 3.7-fold upon lowerin g extracellular pH from 7.5 to 6.5 suggesting the presence of a lactate/pro ton-cotransporter. Antibodies against mono carboxylate transporter 1 (MCT1) reacted positively with plasma membranes (PM), but not with intracellular membranes, prepared from adipocytes. MCT1 expression was down-regulated in PM of adipocytes from diabetic rats, which also displayed a corresponding l oss (similar to 64%) in their capacity to transport lactate. The data suppo rt a role for MCT1 in lactate transport and suggest that changes in MCT1 ex pression are likely to have important implications for adipocyte lactate me tabolism, (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B,V, All rights reserved.