| Objective: Rennin angiotensin aldosterone system (RAS) plays a crucial role in the initiation and development of cardiac remodeling. Angiotensin II(AngII) has multiple physiological effects on the cardiovascular system. In the present study, by using the cultured neonatal rat ventricular myocyte, we examined the change of the cardiomyocytes cell cycle after the AngII stimulation to study the effect of the AngII on cardiomyocytes. The effect and its mechanism of Xin LiKang (XLK), a kind of Chinese herbal compound, on cultured hypertrophy cardiomyocytes stimulated by AngII were also studied.Methods: Partly aorta coarctation was practiced in Wistar rats. 20 days after the coarctation the rats were fed the XLK for 8 days, then gathered the rats' serum and examined by thin-layer chromatography. Neonatal rat ventricular myocytes were digested and separated by collagenase II and trypsin, then purification with differential anchoring. Immunohistochemistry and phase-contrast microscope were used to comprehend the purity, vitality and morphology. MTT experiment, together with phase-contrast microscope was used to evaluate the toxicity of XLK complex on cardiomyocytes. c-Jun protein, Bcl-2 and Bax protein expression were examined by immunocytochemistry. DNA content and cell cycle, as well as apoptosis index were detected by flow cytometric assay. Atrial natriuretic factor (ANP) expression wasidentified by radioimmunoassay.Results: Immunohistochemistry results showed that more than 90% cells were a -sarcometin actin stained positive cells, indicating that the cultures were pure, vigorous and typical cardiomyocytes. (1) No significant difference was found between cardiomyocytes treated with XLK and serum-free medium detected by MTT and phase-contrast microscope. MTT results indicated that incubation with XLK for time from 0 to 24h was not detrimental to cell viability. In the basal state, a little apoptosis was detected by flow cytometric assay. Exposure of myocytes to XLK did not cause significant change in apoptosis index. Cell cycle results showed that XLK altered theamount of basal DNA content in myocytes cultured with the basal medium. (2) In our present study, exposure to AngII produced morphological and biochemical alterations indicative of cardiomyocyte hypertrophy, XLK decreased cardiomyocyte cell size which exposure to AngII obviously; meanwhile Ang II directly stimulates heart rate, which high dosage XLK can decrease obviously; (3) In the Angll group, reexpression of ANP (the "fetal"pattern of gene expression is recapitulated) which has been widely used as an index of hypertrophy, was (780±3 8ng/ml), and the ANP was (430±23ng/ml ) in the control group, respectively. Compared with the Angll group, XLK decreased the reexpression of ANF obviously; (4) By 24hours, Angll treatment caused a marked increase both in G0/G1 and G1/M DNA content, which was coupled with the significantly increased ANP protein expression and enhanced total protein synthesis. XLK treatment significantly suppressed AngII induced DNA synthesis change; (5) After 24 hours' Ang II stimulating, the c-Jun protein of cardiomyocytes increased by 2.8-fold compared with the control group(p<0.05), but in both XLK Group, the level of c-jun of cardiomyocyte decreased obviously compared with the Angll group; (6) To evaluate the effect of Pd-Ia on the molecular circuit controlling apoptosis in cardiac muscle, we observed the expression of Bcl-2 family members including Bcl-2 itself and Bax which may be general mediators of apoptosis in our study. The result showed that that the expression of Bcl-2 was decreased 26% in Angll group compared with control group (p<0.05), while the Bax protein increased by 1.15-fold, the proportion of Bcl-2 and Bax showed significant decreased 35% compared with the control group; XLK obviously increased the Bcl-2 protein in cardiomyocytes; compared with the Ang II group, the expression of Bcl-2 increased by 1.26-fold and 1.21-fold respectively in both high dosage and low dosage XLK group (p<0.05), the proportion of...
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