Mechanisms of the contractile effects of flosequinoxan

N. Zimmermann, G. S. Bodor, P. Boknik, E. Gams, L. R. Jones, J. Neumann, H. Scholz

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Abstract

In guinea-pig papillary muscles the positive inotropic effect of flosequinoxan (BTS) starting at 100 μmol/1 amounted to 287.6 ± 34.2% at 300 μmol/l without any effects on time to peak tension (103.9 ± 2%) and relaxation time (107.1 ± 6.7% of predrug value, respectively). 10 μmol/l carbachol attenuated the positive inotropic effect of 300 μmol/l to 166.5 ± 11.6% (n = 10). The phosphorylation state of the inhibitory subunit of troponin (TnI) and phospholamban(PLB) in [32P]-labeled guinea-pig ventricular myocytes was increased starting at 100 μmol/l amounting to 142.5 ± 12.6% and 130.9 ± 2.2% at 300 μmol/l, respectively (n = 5). Furthermore, BTS (300 μmol/l) decreased phosphorylase phosphatase activity by 23.1%. It is concluded that the contractile effects of BTS are accompanied by enhanced phosphorylation of regulatory proteins which could in part be due to inhibition of phosphorylase phosphatase activity.

Original languageEnglish (US)
Pages (from-to)385-390
Number of pages6
JournalNaunyn-Schmiedeberg's Archives of Pharmacology
Volume351
Issue number4
DOIs
StatePublished - Apr 1 1995

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Zimmermann, N., Bodor, G. S., Boknik, P., Gams, E., Jones, L. R., Neumann, J., & Scholz, H. (1995). Mechanisms of the contractile effects of flosequinoxan. Naunyn-Schmiedeberg's Archives of Pharmacology, 351(4), 385-390. https://doi.org/10.1007/BF00169079