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Relationship of MTT reduction to stimulants of muscle metabolism
journal contribution
posted on 2023-05-16, 12:12 authored by Newman, JMB, DiMaria, CA, Stephen RattiganStephen Rattigan, Steen, JT, Miller, KAL, Eldershaw, TPD, Michael ClarkMichael ClarkMTT, a positively charged tetrazolium salt, is widely used as an indicator of cell viability and metabolism and has potential for histochemical identification of tissue regions of hypermetabolism. In the present study, MTT was infused in the constant-flow perfused rat hindlimb to assess the effect of various agents and particularly vasoconstrictors that increase muscle metabolism. Reduction of MTT to the insoluble formazan in muscles assessed at the end of experiments was linear over a 30 min period and production rates were greater in red fibre types than white fibre types. The vasoconstrictors, norepinephrine (100 nM) and angiotensin (10 nM) decreased MTT formazan production in all muscles but increased hindlimb oxygen uptake and lactate efflux. Veratridine, a Na + channel opener that increases hindlimb oxygen uptake and lactate efflux without increases in perfusion pressure, also decreased MTT formazan production. Membrane stabilizing doses (100 μM) of (±)-propranolol reversed the inhibitory effects of angiotensin and veratridine on MTT formazan production. Muscle contractions elicited by stimulation of the sciatic nerve, reversed the norepinephrine-mediated inhibitory effects on MTT formazan production, even though oxygen consumption and lactate efflux were further stimulated. Stimulation of hindlimb muscle oxygen uptake by pentachlorophenol, a mitochondrial uncoupler, was not associated with alterations in MTT formazan production. It is concluded that apart from muscle contractions MTT formazan production does not increase with increased muscle metabolism. Since the vasoconstrictors angiotensin and norepinephrine as well as veratridine activate Na + channels and the Na +/K + pump, energy required for Na + pumping may be required for MTT reduction. It is unlikely that vasoconstrictors that stimulate oxygen uptake do so by uncoupling respiration. (C) 2000 Elsevier Science Ireland Ltd.
History
Publication title
Chemico-Biological InteractionsVolume
128Pagination
127-140ISSN
0009-2797Department/School
Tasmanian School of MedicinePublisher
Elsevier Science IrelandPlace of publication
IrelandRepository Status
- Restricted