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Muscle Nerve. 2000 Jan;23(1):90-7.

Mutations in MCT1 cDNA in patients with symptomatic deficiency in lactate transport.

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Biochemical Pathology Division, Environmental Pathology Department, Room M093C, Armed Forces Institute of Pathology, Washington, DC 20306-6000, USA.


We identified 5 patients with subnormal erythrocyte lactate transport plus symptoms and signs of muscle injury on exercise and heat exposure. All had transport rates below the 95% envelope for normals. Three cases had rates 40-50% of mean normal. One was found to have a missense mutation in monocarboxylate transporter 1 (MCT1), the gene for the red cell lactate transporter (also expressed in skeletal muscle), at a conserved site, which was not mutated in a cohort of 90 normal humans. The other 2 cases had a different missense mutation (at a nonconserved site), which was also not mutated in the normal cohort. All 3 patients were heterozygotes. We presume that these mutations are responsible for their subnormal lactate transport, and hence their muscle injury under environmental stress; homozygous patients should be more seriously compromised. The other 2 cases had lactate transport rates 60-65% of mean normal, and their MCT1 revealed a third mutation, which proved to be a common polymorphism in the normal cohort. These 2 patients may be physiologic outliers in lactate transport, with their muscle damage arising from some other genetic defect.

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