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

• Published in: Endocrine research 1997-01, Vol.23 (3), p.157-165
• Main Authors: Brtko, Julius, Nedvidková, Jara, Haluzik, Martin, Schreiber, Vratislav
• Format: Article
• Language: English
• Subjects: Animals; Cell Nucleus - metabolism; Dose-Response Relationship, Drug; Liver - drug effects; Liver - ultrastructure; Male; Methylene Blue - administration & dosage; Methylene Blue - pharmacology; Rats; Rats, Wistar; Receptors, Thyroid Hormone - metabolism; Triiodothyronine - metabolism
• ISSN: 0743-5800; 1532-4206
• DOI: 10.3109/07435809709031850

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 μmol/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.