埼玉医科大学雑誌 第34巻 第1号別頁 (2007年10月) T1-T9頁 ◇論文(図表を含む全文)は，PDFファイルとなっています．
PDF (5.3 MB)
医学博士 甲第1017号 平成18年3月24日 （埼玉医科大学）
Cytosolic Calicum Regulation in Ventricular Myocytes of Rats with Monocrotalin-Induced Heart Failure
Monocrotaline (MCT) has been well known to induce pulmonary hypertension (PH) without changing systemic blood pressure in animal models. We previously reported that pathological hypertrophy occurred in left ventricle (LV) as well as in right ventricle (RV) with MCT-induced PH model although neither pressure or volume overload was burdened on LV. Our purpose is to examine differences in [Ca2+]i regulation between hypertrophic myocytes with pressure overload (RV myocytes) and those without pressure overload (LV myocytes). Our working hypothesis was that RV remodeling due to both direct mechanical overload and neurohumoral factors may have different effects on myocyte Ca2+ regulation in comparison with LV remodeling solely due to neurohumoral factors. We injected MCT or control saline intraperitonealy and observed these rats for 6 weeks. We lost some of them due to pump failure or other complications. Ventricular myocytes were isolated enzymatically from RV and LV free walls 6 weeks after injection. We measured [Ca2+]i beat to beat basis using fluo-3 as previously reported. In stabilized electrically-activated [Ca2+]i transients, the peak systolic [Ca2+]i and the amplitude of [Ca2+]i significantly increased in LV myocytes of MCT rats as compared with LV myocytes of Sham rats or RV myocytes of MCT rats. The decline phase of [Ca2+]i transients were also accelerated in LV myocytes of MCT rats. But these parameters were not changed in RV myocytes of MCT rats in comparison with RV myocytes of Sham rats. Protein kinase activation of myocytes increased peak systolic [Ca2+]i but decreased the decline speed of [Ca2+]i transients in both LV and RV of MCT and Sham. The normalized [Ca2+]i transients decline speed was not associated with plasma brain natriuretic peptide level (a well known marker of heart failure grading).