Abstract
Purpose: :
MCT3 is a proton–coupled monocarboxylate transporter expressed in the basolateral membrane of the retinal pigment epithelium (RPE). We hypothesize that the coordinated transport activities of MCT1 in the apical membrane and MCT3 in the basolateral membrane regulate the transport of water, protons and lactate out of the retina thereby regulating the microenvironment of the retina. To investigate the importance of MCT3 in maintaining retinal homeostasis and normal visual function we examined structural and functional changes in retinas of MCT3 null mice.
Methods: :
Standard histological and immunohistochemical, and biochemical methods were used to examine changes morphology and protein expression in retinas from MCT3 null mice and age matched wild type controls. Electroretinography was used to assess retinal function.
Results: :
MCT3 null mice are viable and fertile and do not exhibit any overt phenotypic changes which is consistent with the limited tissue expression of MCT3. The development and the lamination of the retina appear normal even at 7 months of age. MCT3 forms a heteromeric complex with CD147. Immunofluorescence analysis of sections of eyes from MCT3 null mice revealed that there was a loss of CD147 in the basolateral membrane of the RPE. In spite of the normal appearance of the retinas in MCT3 null mice, the amplitudes of the a– and b–waves of the electroretinogram were reduced.
Conclusions: :
The results of the studies support our hypothesis that MCT3 is essential for maintaining normal retinal function. Additionally the results demonstrate that the expression of CD147 in the basolateral membrane of RPE is regulated through its association with MCT3.
Keywords: retinal pigment epithelium • ion transporters • PH regulation/protons