Monocarboxylate transporters and their functions in the retina

Abstract

SummaryMonocarboxylate transporters (MCTs) have important functions in healthy tissues, being involved in the transmembrane transport of lactate and other monocarboxylic acids. MCTs are a family of transporters which is presently composed by 14 members, but only MCT1–4 have been biochemically characterized. MCTs are located in the cornea, iris and ciliary body as well as the retina and pigment epithelium (RPE)/choroid. MCT1 is localized particularly to the apical and MCT3 to the basal membrane of the RPE. MCT1 is located to photoreceptor inner segments, Müller cells, retinal capillaries, and the two plexiform layers. In contrast MCT2 labelling is concentrated in the inner and outer plexiform layers with MCT4 being associated only in the inner nuclear retina and the plexiform layers.In an attempt to understand the role of pyruvate/lactate transport in the retina the influence of a specific MCT inhibitor (4‐cyano‐4‐hydroxycinnamate or 4‐CIN) was tested on ischemia/reperfusion in the rat. No evidence was found to support the view that blockade of lactate/pyruvate entry into mitochondria for oxidative metabolism has an influence on the outcome of retinal ischemia/ reperfusion.