Comparison of in vivo long-term treatment of rats by methylene blue with its in vitro effects on thyroid hormone--nuclear receptor complex formation in liver.
The present study was undertaken to investigate both in vitro effects of methylene blue and its long-term in vivo influence on 3,5,3'-L-triiodothyronine nuclear receptor binding characteristics in rat liver. In vitro, methylene blue at 1 nmol/l was found to inhibit (p < 0.05) the 3,5,3'-L-triiodothyronine (T3) specific binding to its cognate nuclear receptors. Methylene blue at 100 nmol/l significantly (p < 0.05) reduced the thyroid hormone receptor (TR) concentration (expressed as the TR maximal binding capacity). The equilibrium association constant (Ka) of that reduced number of TR resulting from 100 nmol/l methylene blue TR treatment was significantly higher (p < 0.05), when compared to samples without methylene blue. Moreover, the T3 was found to dissociate from the TR-T3 complex in the presence of 1 mumol/l methylene blue. In vivo long-term treatment of rats with 0.125%, 0.25% or 0.5% methylene blue for 28 days did not affect either the TR maximal binding capacity (Bmax) or the Ka values in comparison with rats fed a standard laboratory diet. The data based on both in vitro or in vivo experiments suggest that in spite of a direct and quick in vitro effect of methylene blue on liver TR concentration and/or TR-T3 dissociation, a long-term in vivo treatment of rats by three different methylene blue concentrations does not affect the thyroid hormone receptor status (the concentration and the affinity) in the liver.
Brtko
J
J
Institute of Experimental Endocrinology, Bratislava, Slovak Republic.
Nedvídková
J
J
Haluzík
M
M
Schreiber
V
V
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000187:drug effects / Q000648:ultrastructure*; D008297:Male; D008751:Methylene Blue / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine; D008751:Methylene Blue