MCT1 confirmed in rat striated muscle mitochondria.
Level 5 - mechanism / opinion, no new human data
Bench and animal tissue laboratory study without human clinical data
PubMed 15121743 · doi:10.1152/japplphysiol.00009.2004
What was done
Tested for the presence of monocarboxylate transporter isoform 1 (MCT1) in mitochondria isolated from rat cardiac, soleus, and extensor digitorum longus (EDL) muscles. The authors evaluated three cell fractionation protocols and three distinct MCT1 antibodies (both custom and commercial) using Western blotting. Purity and localization were assessed by co-probing for GLUT1 (sarcolemmal marker), CD147 (chaperone protein), and cytochrome oxidase (inner mitochondrial membrane marker).
What was found
The abstract reports no numerical values. Western blotting demonstrated MCT1 in mitochondrial fractions, sarcolemmal membranes, and whole muscle homogenates across all tested muscle types. These results were consistent across all three MCT1 antibodies and two of the three fractionation methods. Probing for GLUT1 and CD147 confirmed that isolated mitochondrial fractions lacked sarcolemmal contamination, and cytochrome oxidase confirmed mitochondrial localization.
Why it matters
Confirms mitochondrial localization of MCT1 in rat muscle, providing support for the intracellular lactate shuttle hypothesis and indicating that prior conflicting reports likely stemmed from cell fractionation artifacts.
Limits
The study was performed exclusively on isolated rat muscle preparations, and the abstract does not report sample sizes (n) or quantitative effect sizes. In vitro fractionation is susceptible to technical artifacts, as evidenced by discordant results in one of the three fractionation methods evaluated.
Cited by
- supports Lactate transporters are located in plasma membranes and within the mitochondrial reticulum as lactate/pyruvate transporters.