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purpose. The neural retina expresses multiple monocarboxylate transporters (MCTs) that are likely to play a key role in the metabolism of the outer retina. Recently, it was reported that targeting of MCT1 and-4 to the plasma membrane requires association with 5A11/basigin (CD147). In the present study, the hypothesis that reduced amplitudes in the electroretinograms in the 5A11/basigin null mouse (Bsg−/−) may be linked to altered expression of MCTs was studied.

methods. The expression and subcellular distribution of MCTs in Bsg−/− mice was analyzed by immunofluorescence microscopy with isoform-specific antibodies. Protein expression was analyzed by Western blot analysis, and mRNA expression was examined with RT-PCR.

results. Immunofluorescence labeling of tissue sections from the Bsg−/− mice revealed a dramatic reduction in labeling with MCT antibodies. There was a loss of MCT1 labeling in the apical membrane of the RPE and in the neural retina. MCT3, which is expressed in the basolateral membrane of the RPE wild-type mouse, was expressed at very low levels in both the apical and basolateral membranes of the Bsg−/− mouse. There was no change in expression or distribution of the glucose transporter (GLUT)-1 in the RPE and retina of the Bsg−/− mouse. Western blot analysis of detergent-soluble lysates prepared from wild-type and Bsg−/− eyes confirmed that the levels of MCT1, MCT3, and MCT4 protein were severely reduced in Bsg−/− mice. RT-PCR analyses of mRNA levels from wild-type and Bsg−/− mice demonstrated that the MCT1 transcript was expressed at normal levels in Bsg−/− mice.

conclusions. In Bsg …