title: Phosphorylation status of regulatory proteins and functional characteristics in myocardium of dilated cardiomyopathy of Syrian hamsters.
abstract: To understand the pathophysiology of hereditary cardiomyopathy, we measured the phosphorylation status of regulatory proteins, troponin I (TnI), troponin T (TnT), myosin light chain 2 (MLC2), and myosin-binding protein C (MyBP-C), and the Ca2+-dependence of tension development and ATPase activity in skinned right ventricular trabeculae obtained from cardiomyopathic (TO-2 strain, n = 8) and control (F1B strain, n = 8) hamsters. The Ca2+ sensitivities of tension development and ATPase activity (mean +/- SD) were significantly (P < 0.0001) higher in the TO-2 strain (pCa50 5.64 +/- 0.04 in tension and 5.65 +/- 0.04 in ATPase activity) than in the F1B strain (pCa50 5.48 +/- 0.03 in tension and 5.51 +/- 0.03 in ATPase activity). No significant differences in their maximum values were observed between TO-2 (40.8 +/- 7.4 mN/mm2 in tension and 0.52 +/- 0.15 micromol/l/s in ATP consumption) and F1B (42.3 +/- 8.5 mN/mm2 in tension and 0.58 +/- 0.41 micromol/l/s in ATP consumption) preparations, indicating that the tension cost (ATPase activity/tension development) in TO-2 was quite similar to that in F1B. The phosphorylation levels of MLC2 and TnI were significantly (P < 0.01) lower in TO-2 than in F1B. These results suggest that the increase in the Ca2+ sensitivities of tension development and the ATPase activity in TO-2 hearts result from the decreased basal level of TnI phosphorylation, and these features can be considered to produce the incomplete diastolic relaxation and partly improve the systolic function in TO-2 hearts.
authors.affiliation: Department of Physiology, Tsurumi University School of Dental Medicine, Tsurumi-ku, Yokohama, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Ohnuki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nishimura
authors.forename: Seiryo
authors.initials: S
authors.lastname: Sugiura
authors.forename: Yasutake
authors.initials: Y
authors.lastname: Saeki
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D024722:Cardiac Myosins / Q000378:metabolism; D002311:Cardiomyopathy, Dilated / Q000378:metabolism* / Q000503:physiopathology*; D002352:Carrier Proteins / Q000378:metabolism; D006224:Cricetinae; D003971:Diastole / Q000502:physiology; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008647:Mesocricetus; D009124:Muscle Proteins / Q000378:metabolism*; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation; D013599:Systole / Q000502:physiology; D019210:Troponin I / Q000378:metabolism; D020107:Troponin T / Q000378:metabolism; D000099163:Myosin Binding Protein C
chemical_list: D000251:Adenosine Triphosphatases; D002118:Calcium; D024722:Cardiac Myosins; D002352:Carrier Proteins; D009124:Muscle Proteins; D018994:Myosin Light Chains; D019210:Troponin I; D020107:Troponin T; D000099163:Myosin Binding Protein C; C107184:myosin light chain 2