Figure 6. Cellular locations of MCT1 and MCT2 lactate transporter isoforms and the mitochondrial reticulum (cytochrome oxidase, COX) in adult rat plantaris muscle determined using confocal laser scanning microscopy (CLSM) and fluorescent probes for the respective proteins.

Comparisons for MCT1 are shown in the first row (A1–A3), and for MCT2 in the second row (B1–B3). The localization of COX was detected in rat plantaris muscle (A1 and B1). MCT1 was detected throughout the cells including subsarcolemmal (arrowheads) and interfibrillar (arrows) domains (A2). MCT1 abundance was greatest in oxidative fibres where COX is abundant and the signal strong. When these MCT1 (green) and COX (red) were merged, superposition of the two probes was clear (yellow), a finding prominent at interfibrillar (arrows) as well as sarcolemmal (arrowheads) cell domains (A3). In contrast, the signal for MCT2 (B2) was weak, relatively more noticeable in fibres denoted by strong staining for COX (B1 and B3, broken line is delineated around oxidative fibre to distinguish the faint signal for MCT2). Overlap of MCT2 and COX is insignificant, denoted by absence of yellow in B3. Scale bar = 50 μm. Sections are from the same animal. Reprinted from Hashimoto et al. (2005).