| AIM (1) To study the role of prostaglandin F2α (PGF2α) in cardiac hypertrophy and its relation with calcineurin (CaN) signal transduction pathway in vivo, in vitro and in molecular levels. (2) To investigate the effects and mechanisms of ginsenoside Rb1 (Rb1) to inhibit the cardiac hypertrophy. METHODS Male Sprague Dawley rats were given a single i.p. injection with monocrotaline (MCT, 60 mg/kg) then fed for 2 weeks (M2W) or 4 weeks (M4W) for inducing compensatory right ventricular hypertrophy (RVH) model. The RVH establishment was confirmed by calculating the RVH index [RVHI, right ventricle (RV)/left ventricle (LV)+septum (S)], RV/body weight (BW), and the atrial natriuretic factor (ANF) expression at mRNA level, and by observing the histological changes with a transmission electron microscope. The pulmonary arterial hypertension (PAH) was ascertained indirectly by lung/BW ratio. In vitro, the cardiomyocyte hypertrophic response was assayed by observing the histological changes and measurement of cell diameter, protein content, and ANF mRNA expression. For mechanism studies, we determined the following parameters using different methods: (1) the intracellular free calcium concentration ([Ca2+]i ) was measured by using Fura 2/AM as a fluorescent indicator; (2) the cardiac tissue PGF2α levels were measured with EIA Kit; (3) ANF and CaN mRNA expressions were determined using reverse transcription-polymerase chain reaction(RT-PCR);(4) CaN, and its downstream effectors, nuclear factor of activated T cell 3 (NFAT3) and GATA4 protein expressions were detected by Western blot; ⑸ except using Rb1 to investigate it's antihypertrophic effects and mechanisms in vivo and in vitro, the following agents were used according to different experimental aims: celecoxib (Cel), a cyclooxygenase inhibitor ;cyclosporin A (CsA), a calcineurin inhibitor;L-arginine, a nitric oxide donor;and NG-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide synthase inhibitor. RESULTS (1) In M2W and M4W groups,the RVHI, RV/BW, and lung/BW were significantly increased by 47 %, 53 %,118 % and 64 %, 94 %,156 %,respectively,compared with vehicle control (p﹤0.001, n=10),some histological injuries were found in RV tissue, and the ANF mRNA expression was significantly increased in both groups. The PGF2αlevels in RV tissue were increased by 44 % in M2W and by 51 % in M4W (p﹤0.05, n=6), which was positively correlated with RVHI, and the expression of ANF mRNA. The expressions of CaN mRNA and CaN, NFAT3 and GATA4 proteins were increased with a manner of positive correlation to PGF2α levels (p﹤0.05, n=3). Administration of Cel from d 1 to d 14 (PC2W group) or from d 15 to d 28 (TC2W group) after MCT injection could obviously decrease the RVHI, RV/BW, and lung/BW when compared with M2W and M4W(p ﹤ 0.05). (2) In vitro, PGF2α significantly increased the cell diameter, protein content and [Ca2+]i in cultured cardiomyocytes with a concentration-dependent manner (p﹤0.001). The hypertrophic morphology changes occurred, such as the cells displayed swollen, and with undistinguishable border. It was similar to the results from animal model that the ANF and CaN mRNA expressions and the protein expressions of CaN / NFAT3 / GATA4 were significantly increased by PGF2α in cultured cardiomyocytes. CsA,a CaN inhibitor,could markedly block the myocyte hypertrophy,blunt the increased [Ca2+]i ,and decrease the expressions of CaN mRNA and CaN / NFAT3 / GATA4 proteins . (3) In MCT-induced hypertrophic model, prevention(from d 1 to d 14 after MCT injection)with Rb1(10mg/kg/d, 20 mg/kg/d, and 40 mg/kg/d)(PR10, PR20, PR40 groups) and L-arginine ( 200 mg/kg/d ) (PL2W group) significantly relieved the cardiac hypertrophy (p ﹤ 0.05) and improved the lung/BW ratio. Somehistological injuries of RV tissue were ameliorated in PR40 group. Similar results were obtained from treatment (from d 15 to d 28 after MCT injection)with Rb1 (10 mg/kg/d, 40 mg/kg/d)(TR10, TR40 groups) and L-arginine (200 mg/kg/d)(TL2W group). The effects on RVHI and lung/BW in TR40 group were better...
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