caa a22 4500 477119387 CHVBK 20180405111631.0 cr unu---uuuuu 170330e19960301xx s 000 0 eng 10.1007/BF00240028 doi (NATIONALLICENCE)springer-10.1007/BF00240028 E-1020, a water soluble imidazopyridine, has direct effects on Ca2+-dependent force and ATP hydrolysis of canine and bovine cardiac myofilaments [Elektronische Daten] [Frances Powers, Kimberly Palmiter, R. Solaro] E-1020 is a cardiotonic agent that acts as a cyclic-AMP phosphodiesterase inhibitor but also may have actions which alter myofilament response to Ca2+. To identify direct actions of E-1020 on cardiac contractile proteins, effects of E-1020 on myofibrillar Ca2+ dependent MgATPase and force generation in chemically skinned fiber bundles were measured. In bovine cardiac myofibrils, E-1020 (100 μM) significantly increased myofilament Ca2+ sensitivity and Ca2+-dependent ATPase activity at submaximal pCa values. At pCa 6.75, E-1020 significantly increased ATPase activity in bovine (10-100 pM) and canine (1-100 pM) cardiac myofibrils but had no effect on rat cardiac myofibrils. Moreover, in one population of canine ventricular fiber bundles, E-1020 (0.0-10 μM) significantly increased isometric tension at pCa 6.5 and 6.0, whereas in another population of bundles E-1020 had no effect on tension. In no case was resting (pCa 8.0) or maximal tension (pCa 4.5) increased by E-1020. Measurements of Ca2+ binding to canine ventricular skinned fiber preparations demonstrated that E-1020 does not alter the affinity of myofilament troponin C for Ca2+. We conclude that part of the mechanism by which E-1020 acts as an inotropic agent may involve alterations in the responsiveness of contractile proteins to Ca2+. The lack of effect of E-1020 on some preparations may be dependent on isoform populations of myofilament proteins. Kluwer Academic Publishers, 1996 E-1020 nationallicence calcium sensitivity nationallicence myofibrillar ATPase activity nationallicence skinned fiber bundles nationallicence isometric tension nationallicence Powers Frances Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, 60680, Chicago, Illinois, USA aut Palmiter Kimberly Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, 60680, Chicago, Illinois, USA aut Solaro R. Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, 60680, Chicago, Illinois, USA aut Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www.wkap.nl 160-161/1(1996-03-01), 33-39 0300-8177 160-161:1<33 1996 160-161 11010 https://doi.org/10.1007/BF00240028 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00240028 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Powers Frances Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, 60680, Chicago, Illinois, USA aut NATIONALLICENCE 700 1- Palmiter Kimberly Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, 60680, Chicago, Illinois, USA aut NATIONALLICENCE 700 1- Solaro R. Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, 60680, Chicago, Illinois, USA aut NATIONALLICENCE 773 0- Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www.wkap.nl 160-161/1(1996-03-01), 33-39 0300-8177 160-161:1<33 1996 160-161 11010 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer