Cell Biology and Toxicology

, Volume 22, Issue 4, pp 257–268 | Cite as

Effect of thioridazine on gap junction intercellular communication in connexin 43-expressing cells

  • D. F. Matesic
  • D. N. Abifadel
  • E. L. Garcia
  • M. W. Jann


Propagation of electrical activity between myocytes in the heart requires gap junction channels, which contribute to coordinated conduction of the heartbeat. Some antipsychotic drugs, such as thioridazine and its active metabolite, mesoridazine, have known cardiac conduction side-effects, which have resulted in fatal or nearly fatal clinical consequences in patients. The physiological mechanisms responsible for these cardiac side-effects are unknown. We tested the effect of thioridazine and mesoridazine on gap junction-mediated intercellular communication between cells that express the major cardiac gap junction subtype connexin 43. Micromolar concentrations of thioridazine and mesoridazine inhibited gap junction-mediated intercellular communication between WB-F344 epithelial cells in a dose-dependent manner, as measured by fluorescent dye transfer. Kinetic analyses demonstrated that inhibition by 10 μmol/L thioridazine occurred within 5 min, achieved its maximal effect within 1 h, and was maintained for at least 24 h. Inhibition was reversible within 1 h upon removal of the drug. Western blot analysis of connexin 43 in a membrane-enriched fraction of WB-F344 cells treated with thioridazine revealed decreased amounts of unphosphorylated connexin 43, and appearance of a phosphorylated connexin 43 band that co-migrated with a “hyperphosphorylated” connexin 43 band present in TPA-inhibited cells. When tested for its effects on cardiomyocytes isolated from neonatal rats, thioridazine decreased fluorescent dye transfer between colonies of beating myocytes. Microinjection of individual cells with fluorescent dye also showed inhibition of dye transfer in thioridazine-treated cells compared to vehicle-treated cells. In addition, thioridazine, like TPA, inhibited rhythmic beating of myocytes within 15 min of application. In light of the fact that the thioridazine and mesoridazine concentrations used in these experiments are in the range of those used clinically in patients, our results suggest that inhibition of gap junction intercellular communication may be one factor contributing to the cardiac side-effects observed in some patients taking these medications.


thioridazine gap junction connexin 43 myocytes 



bovine serum albumin


dimethyl sulfoxide


nitroblue tetrazolium/5-bromo-4-chloro-3-indoyl phosphate


phosphate-buffered saline


phenylmethylsulfonyl fluoride


polyvinylidene fluoride


sodium dodecyl sulfate


phorbol 12-myristate 13-acetate


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  1. Beyer E, Paul DL, Goodenough DA. Connexin43: a protein from rat heart homologous to a gap junction protein from liver. J Cell Biol. 1987;105:2621–9.PubMedCrossRefGoogle Scholar
  2. Britz-Cunningham SH, Shah MN, Zuppan CW, Fletcher WH. Mutations of the connexin43 gap-junction gene in patients with heart malformations and defects of laterality. N Engl J Med. 1995;332:1323–9.PubMedCrossRefGoogle Scholar
  3. Buckley NA, Whyte IM, Dawson AH. Cardiotoxicity more common in thioridazine overdose than with other neuroleptics. J Toxicol Clin Toxicol. 1995;33:199–204.PubMedGoogle Scholar
  4. Budunova IV, Williams GM, Spray DC. Effect of tumor promoting stimuli on gap junction permeability and connexin43 expression in ARL 18 rat liver cell line. Arch Toxicol. 1993;67:565–72.PubMedCrossRefGoogle Scholar
  5. Dallaire S. Thioridazine (Mellaril) and mesoridazine (Serentil): prolongation of the QTc interval. Can Med Assoc J. 2001;164:91.Google Scholar
  6. Dhein S. Gap junction channels in the cardiovascular system: pharmacological and physiological modulation. Trends Pharmacol Sci. 1998;19:229–41.PubMedCrossRefGoogle Scholar
  7. Gros DB, Jongsma HJ. Connexins in mammalian heart function. BioEssays. 1996;18:719–30.PubMedCrossRefGoogle Scholar
  8. Hale PW Jr, Poklis A. Thioridazine-5-sulfoxide cardiotoxicity in the isolated perfused rat heart. Toxicol Lett. 1984;21:1–8.PubMedCrossRefGoogle Scholar
  9. Hale PW Jr, Poklis A. Cardiotoxicity of thioridazine and two stereoisomeric forms of thioridazine 5-sulfoxide in the isolated perfused rat heart. Toxicol Appl Pharmacol. 1986;86:44–55.PubMedCrossRefGoogle Scholar
  10. Hale PW Jr, Poklis A. Thioridazine cardiotoxicity. J Toxicol Clin Toxicol. 1996;34:127–30.PubMedCrossRefGoogle Scholar
  11. Huston JR, Bell GE. The effect of thioridazine hydrochloride and chlorpromazine on the electrocardiogram. JAMA. 1966;198:134–38.PubMedCrossRefGoogle Scholar
  12. Kelly HQ, Fay JE, Laverty FG. Thioridazine hydrochloride (Mellaril): its effect on the electrocardiogram and a report on two fatalities. Can Med Assoc J. 1963;89:546–54.PubMedGoogle Scholar
  13. Laird DW, Revel JP. Biochemical and immunochemical analysis of the arrangement of connexin43 in rat heart gap junction membranes. J Cell Sci. 1990;97(Pt 1):109–17.PubMedGoogle Scholar
  14. Lampe PD, TenBroek EM, Burt JM, Kurata WE, Johnson RG, Lau AF. Phosphorylation of connexin43 on serine368 by protein kinase C regulates gap junctional communication. J Cell Biol. 2000;149:1503–12.PubMedCrossRefGoogle Scholar
  15. Manjunath CK, Goings GE, Page E. Cytoplasmic surface and intramembrane components of rat heart gap junctional proteins. Am J Physiol. 1984;246:H865–75.PubMedGoogle Scholar
  16. Martensson E, Nyberg G, Axelsson R. Quantitative determination of thioridazine and nonconjugated thioridazine metabolites in serum and urine of psychiatric patients. Curr Ther Res. 1975;18:687–700.PubMedGoogle Scholar
  17. Matesic DF, Rupp HL, Bonney WJ, Ruch RJ, Trosko JE. Changes in gap-junction permeability, phosphorylation, and number mediated by phorbol ester and non-phorbol-ester tumor promoters in rat liver epithelial cells. Mol Carcinog. 1994;10:226–36.PubMedGoogle Scholar
  18. Musil LS, Goodenough DA. Biochemical analysis of connexin43 intracellular transport, phosphorylation, and assembly into gap junctional plaques. J Cell Biol. 1991;115:1357–74.PubMedCrossRefGoogle Scholar
  19. Page E. Cardiac gap junctions. In: Fozzard HS et al., eds. The heart and cardiovascular system. New York: Raven Press; 1992:1003–48.Google Scholar
  20. Reaume AG, de Sousa PA, Kulkarni S, et al. Cardiac malformation in neonatal mice lacking connexin43. Science. 1995;267:1831–34.PubMedGoogle Scholar
  21. Rohr S. Role of gap junctions in the propagation of the cardiac action potential. Cardiovasc Res. 2004;62:309–22.PubMedCrossRefGoogle Scholar
  22. Severs NJ. Cardiac muscle cell interaction: from microanatomy to the molecular make-up of the gap junction. Histol Histopathol. 1995;10:481–501.PubMedGoogle Scholar
  23. Trosko JE, Chang CC, Madhukar BV. In vitro analysis of modulators of intercellular communication: implications for biologically based risk assessment models for chemical exposure. Toxicol In Vitro. 1990;4:635–43.CrossRefPubMedGoogle Scholar
  24. Tsao MS, Smith JD, Nelson KG, Grisham JW. A diploid epithelial cell line from normal adult rat liver with phenotypic properties of “oval” cells. Exp Cell Res. 1984;154:38–52.PubMedCrossRefGoogle Scholar
  25. Von Bahr C, Movin G, Nordin C, et al. Plasma levels of thioridazine and metabolites are influenced by the debrisoquin hydroxylation phenotype. Clin Pharmacol Ther. 1991;49:234–240.CrossRefGoogle Scholar
  26. Vozzi C, Dupont E, Coppen SR, Yeh HI, Severs NJ. Chamber-related differences in connexin expression in the human heart. J Mol Cell Cardiol. 1999;31:991–1003.PubMedCrossRefGoogle Scholar
  27. Willecke K, Elberger J, Degen J, et al. Structural and functional diversity of connexin genes in the mouse and human genome. Biol Chem. 2002;383:25–37.CrossRefGoogle Scholar

Copyright information

© Springer Science + Business Media, Inc. 2006

Authors and Affiliations

  • D. F. Matesic
    • 1
    • 2
  • D. N. Abifadel
    • 1
  • E. L. Garcia
    • 1
  • M. W. Jann
    • 1
  1. 1.Southern School of PharmacyMercer UniversityAtlantaUSA
  2. 2.Department of Pharmaceutical SciencesMercer UniversityAtlantaUSA

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