Thyroxine reversibly inhibits the uncoupling action of protonophores on energy production in rat thymus lymphocytes.
Earlier we reported that some thyroid and steroid hormones and also 6-ketocholestanol used in micromolar concentrations modulated the effects of protonophoric uncouplers on isolated mitochondria (Starkov et al. (1997) Biochim. Biophys. Acta, 1318, 173-183). In the present study we investigated the effects of a thyroid hormone, thyroxine, on energy coupling of intact rat thymus lymphocytes and mitochondria isolated from these cells. The resting (oligomycin-inhibited) respiration of the isolated intact lymphocytes was stimulated by the addition of protonophoric uncouplers 2,4-DNP, FCCP, or SF6847. Subsequent addition of micromolar concentrations of thyroxin decreased the rate of uncoupler-stimulated respiration and partially reversed uncoupler-induced decrease of membrane potential (DeltaPsi). In experiments with mitochondria isolated from thymus lymphocytes the re-coupling effect of thyroxine was not observed. In this case thyroxine did not influence mitochondrial respiration stimulated with 2,4-DNP, but did potentiate the stimulation of respiration and DeltaPsi decrease induced with another uncoupler, SF6847. The data are discussed in terms of a hypothesis that aromatic uncouplers are transported into the cell by the thyroxine carrier of the plasma membrane.
Palamarchuk
L A
LA
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899, Russia. mansur@genebee.msu.su
Mansurova
S E
SE
Starkov
A A
AA
D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D004734:Energy Metabolism / Q000187:drug effects*; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology*; D008214:Lymphocytes / Q000378:metabolism* / Q000648:ultrastructure; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology; D009570:Nitriles / Q000494:pharmacology; D011522:Protons; D051381:Rats; D013950:Thymus Gland / Q000166:cytology*; D013974:Thyroxine / Q000494:pharmacology*; D014475:Uncoupling Agents / Q000494:pharmacology*
D007476:Ionophores; D009570:Nitriles; D011522:Protons; D014475:Uncoupling Agents; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; C001784:SF 6847; D019297:2,4-Dinitrophenol; D013974:Thyroxine