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. 1981 Apr;44(1):211–219.

The uptake of tritium-labelled carnitine by monolayer cultures of human fetal muscle and its potential as a label in cytotoxicity studies

Geraldine Cambridge, C M M Stern
PMCID: PMC1537228  PMID: 7261477

Abstract

As a novel approach to the investigation of immune responses directed against muscle antigens in inflammatory muscle disease, the use of tritium-labelled carnitine as a selective marker for myotubes in monolayer cultures was investigated. Tritium-labelled carnitine was incubated either with monolayer cultures of human fetal muscle (which contain fibroblasts and myotubes) or with syngeneic monolayer cultures of human fetal fibroblasts. The rate of uptake and loss of tritium-labelled carnitine by muscle cultures was compared with that shown by fibroblast cultures; uptake being five times greater for muscle. Values for Km and Vmax were derived for both tissues in culture, the ratio Km/Vmax being 3·1 for muscle cultures and 0·46 for fibroblast cultures, indicating the presence of the active transport system for carnitine in the myotube membrane. Freeze-dried radioautographs of muscle monolayers, previously incubated with tritium-labelled carnitine, were made and confirmed the specific intra-tubular localization of the label. Fetal muscle monolayers, previously incubated with tritium-labelled carnitine, were used as targets in long-term cytotoxicity experiments into lymphocyte-mediated myotoxicity. Peripheral blood lymphocytes from patients with inflammatory muscle disease were shown to be myotoxic, but lymphocytes from normal individuals or those with non-inflammatory muscle disease were not. This system is likely to prove much more sensitive than those methods employing chromium-51-labelled cultures. Carnitine-based measures of myotoxicity closely followed the clinical activity of the disease in sequential studies carried out on one patient and the test shows considerable potential as a means of assessing myotube killing by lymphocytes on a per-cell basis.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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