Effect of diclofenac on SLC16A3/MCT4 by the Caco-2 cell line.

In the present study, we demonstrated that monocarboxylate transporter 4 (MCT4) is functionally expressed in Caco-2 cells. We studied the effects of 4 nonsteroidal anti-inflammatory drugs on the uptake of l-lactate as a good substrate of MCT4 by the cells. The monocarboxylate drugs inhibited the uptake of l-lactate into the cells. Diclofenac, as a member of the aryl-acetic acid group of nonsteroidal anti-inflammatory drugs, was the most potent inhibitor, with an inhibition constant of 20 μM. In the next study, we determined the type of inhibition for diclofenac. An l-lactate carrier is non-competitively inhibitable by the drug. We also demonstrated, in Xenopus oocyte expression system, potential of diclofenac for MCT4 inhibitor. The present results could provide a useful tool to discover MCT4-specific inhibitors.