Effect of thymol on calcium handling in mammalian ventricular myocardium

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Concentration-dependent effects of thymol on calcium handling were studied in canine and guinea pig cardiac preparations (Langendorff-perfused guinea pig hearts, canine ventricular trabeculae, canine sarcoplasmic reticular vesicles and single ryanodine receptors). Thymol induced a concentration-dependent negative inotropic action in both canine and guinea pig preparations (EC 50 = 297 ± 12 μM in dog). However, low concentrations of thymol reduced intracellular calcium transients in guinea pig hearts without decreasing contractility. At higher concentrations both calcium transients and contractions were suppressed. In canine sarcoplasmic reticular vesicles thymol induced rapid release of calcium (Vmax = 0.47 ± 0.04 nmol s-1, EC50 = 258 ± 21 μM, Hill coefficient = 3.0 ± 0.54), and decreased the activity of the calcium pump (EC50 = 253 ± 4.7 μM, Hill coefficient = 1.62 ± 0.05). Due to the less sharp concentration-dependence of the ATPase inhibition, this effect was significant from 50 μM, whereas the thymol-induced calcium release only from 100 μM. In single ryanodine receptors incorporated into artificial lipid bilayer thymol induced long lasting openings, having mean open times increased with 3 orders of magnitude, however, the specific conductance of the channel remained unaltered. This effect of thymol was not voltage-dependent and failed to prevent the binding of ryanodine. In conclusion, the negative inotropic action of thymol can be explained by reduction in calcium content of the sarcoplasmic reticulum due to the combination of the thymol-induced calcium release and inhibition of the calcium pump. The calcium-sensitizer effect, observed at lower thymol concentrations, indicates that thymol is likely to interact with the contractile machinery also.

Original languageEnglish
Pages (from-to)909-921
Number of pages13
JournalLife Sciences
Volume74
Issue number7
DOIs
Publication statusPublished - Jan 2 2004

Fingerprint

Thymol
Myocardium
Calcium
Canidae
Guinea Pigs
Ryanodine Receptor Calcium Release Channel
Pumps
Ryanodine
Lipid bilayers
Lipid Bilayers
Sarcoplasmic Reticulum
Machinery
Adenosine Triphosphatases

Keywords

  • Cardiac cells
  • Intracellular calcium transients
  • Ryanodine receptor
  • Sarcoplasmic reticulum
  • Thymol

ASJC Scopus subject areas

  • Pharmacology

Cite this

Effect of thymol on calcium handling in mammalian ventricular myocardium. / Szentandrássy, N.; Szigeti, G.; Szegedi, C.; Sárközi, S.; Magyar, J.; Bányász, Tamás; Csernoch, L.; Kovács, László; Nánási, P.; Jóna, I.

In: Life Sciences, Vol. 74, No. 7, 02.01.2004, p. 909-921.

Research output: Contribution to journalArticle

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abstract = "Concentration-dependent effects of thymol on calcium handling were studied in canine and guinea pig cardiac preparations (Langendorff-perfused guinea pig hearts, canine ventricular trabeculae, canine sarcoplasmic reticular vesicles and single ryanodine receptors). Thymol induced a concentration-dependent negative inotropic action in both canine and guinea pig preparations (EC 50 = 297 ± 12 μM in dog). However, low concentrations of thymol reduced intracellular calcium transients in guinea pig hearts without decreasing contractility. At higher concentrations both calcium transients and contractions were suppressed. In canine sarcoplasmic reticular vesicles thymol induced rapid release of calcium (Vmax = 0.47 ± 0.04 nmol s-1, EC50 = 258 ± 21 μM, Hill coefficient = 3.0 ± 0.54), and decreased the activity of the calcium pump (EC50 = 253 ± 4.7 μM, Hill coefficient = 1.62 ± 0.05). Due to the less sharp concentration-dependence of the ATPase inhibition, this effect was significant from 50 μM, whereas the thymol-induced calcium release only from 100 μM. In single ryanodine receptors incorporated into artificial lipid bilayer thymol induced long lasting openings, having mean open times increased with 3 orders of magnitude, however, the specific conductance of the channel remained unaltered. This effect of thymol was not voltage-dependent and failed to prevent the binding of ryanodine. In conclusion, the negative inotropic action of thymol can be explained by reduction in calcium content of the sarcoplasmic reticulum due to the combination of the thymol-induced calcium release and inhibition of the calcium pump. The calcium-sensitizer effect, observed at lower thymol concentrations, indicates that thymol is likely to interact with the contractile machinery also.",
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AU - Szigeti, G.

AU - Szegedi, C.

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AU - Magyar, J.

AU - Bányász, Tamás

AU - Csernoch, L.

AU - Kovács, László

AU - Nánási, P.

AU - Jóna, I.

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