| Heart failure is a terminal stage of many kinds of heart diseases. Because of its high rate of disability and mortality, HF is becoming one of the serious public health problems in the 21'st century. So it's important to pay more attention to its fundamental and clinical researches.Many causes, such as chronic pressure overload, chronic volume overload and cardiomyopathy account for HF .There are 3 stages(phases) of HF's development: primarily hemodynamics changes, adaptational cardiac hypertrophy, terminally maladaptive and HF .At the early stage of HF development, adaptive cardiomyocyte hypertrophy, provides a short-term mechanism to improve contractile performance and decrease wall stress, can maintain the normal heart function. However, with the disease program prolonged, the hypertrophic program becomes maladaptive and turns to heart failure, resulting in decreased contractile function and enhancing cardiomyocyte apoptosis and fibrosis. Now, although there are many researches focusing on the transition from cardiac hypertrophy to heart failure, the mechanism is still not clear. Recent resaeaches suggested that decreased contractility of cardiomyocyte may play an important role in the decreasedcardiac function during the transition from cardiac hypertrophy to heart failure . Other researches indicated that the loss of cardiomyocyte due to the cardiomyocyte apoptosis may take part in heart failure. So it is important to elucidate the time course of change in contractility of hypertrophic cardiomyocytes.To answer those questions mentioned above, we took spontaneously hypertensive rat as a cardiac hypertrophy and heart failure model. Valid adult rat cardiomyocyte isolation technique was established. The length and width of cardiomyocyte were detected by Edge-Detector System, the unloaded contractile signal was collected and analyzed by Felix software.We observed the unload contractile function about 4-month and 10-month old SHR and WKY rat. The main results were as fellows:1) Establishing a valid adult rat cardiomyocyte isolation technique The rat's heart was mounted on a Langendorff perfusion apparatus with low perfusion pressure and low flow velocity. The rod-shaped cardiomyocytes were 75~85% among the freshly isolated cardiomyocyte, then reduced to 40-45% after resumed Ca 2+. After 4-h ,the rod-shaped cardiomyocytes were 25~35%. The rod-shaped cardiomyocytes were quiescent , visible cross striations ,having sharp edges and normal unload shorten function. The result suggested the isolation techniqu was valid and the isolated cardiomyocytes could be used in the fellow tests.2) Detecting the systolic pressure and cell area of SHR The systolic pressure of SHR and WKY was measured by Tail-cuff. Compared with the WKY,the systolic pressure of SHR was significantly increased, which began to be over 150 mmHg when the male SHR at 3-month old. And the cardiomyocyte area of 4-month SHR (median was 2902. 1μm2) wassignificantly increased than that of WKY (median was 1540.1μm2). The cardiomyocyte area of 10-month SHR (median was 3266.1μm2) was increased than that of 4-month SHR ,but having no statistic meaning(P>0.05).3) Shortening amplitude-frequency relationship of hypertrophic cardiomyocyte Shortening amplitude of WKY cardiomyocyte was significantly increased with the stimulation frequency, 10.70%±0.28% at 1Hz stimulation, 11.43%±0.25% at 2Hz stimulation and 11.02%±0.22% at 3Hz stimulation. Shortening amplitude of 4-month SHR cardiomyocyte was not significant increased with the stimulation frequency, but compared with that of WKY, SHR's shortening amplitude was significant incrased at 1Hz stimulation (11.66%±0.36%) and 3Hz stimulation (11.83%±0.31%), at 2 Hz stimulation (11.71 %±0.25 %)was not obvious. Shortening amplitude of 10-month SHR cardiomyocyte was obviously decreased, 10.64%±0.42% at lHz stimulation, 10.35%±0.29% at 2Hz stimulation, 9.44%±0.28% at 3Hz stimulation. Shortening amplitude of 10-month SHR cardiomyocyte was significant decreased than that of 4-month SHR and WKY, except that at 1Hz stimulation with WKY.4) The changes in the cardiomyocytes unloaded contractile's duration and rate The hypertrophic cardiomyocyte contractile duration was longer than that of WKY. When the stimulation was at 1Hz, 2Hz, 3Hz, the TPS of WKY was 128.42±4.04ms, 115.58±2.93ms and 100.00±2.20ms separately, while the correspond TPS of 4-month SHR was 143.91±2.00ms, 130.87±1.16ms, 116.96±1.02ms and the correspond TPS of 10-month SHR was 139.86±2.65ms, 123.03±2.52ms, 107.00±2.29ms. At the stimulation condition, the TR90 of WKY was 102.27±2.15ms, 96.63±2.66ms and 87.50±2.14ms separately, while the correspond TR90 of 4-month SHR was 115.00±2.27ms,ms, 87.92±1.72 ms and the correspond TR90 of 10-month SHR was 17.74±3.10 ms, 98.52±0.85 ms, 91.67±0.72 ms. The shortening and relengthening rate of both SHR and WKY increased with the stimulation frequency increased. But the rate of SHR was lower than that of WKY at the same stimulation frequency.5)The effects of PMA and Staurosporine on the cardiomyocyte unloaded contractile function PMA inhibit the cardiomyocyte unload contractile function. Exposured to 50 nmol/L,100 nmol/L and 200 nmol/L PMA, the shortening amplitude of WKY cardiomyocyte was decreased to 69. 79%±1.90 %, 58.22%±2.16% and 22.67%±2.52%,separately, while that of 4-month SHR cardiomyocyte was decreased to 6.07%±0.69%, 2.40%±0.22%, 12.47 %±2.60%. Shortening amplitude of 10-month SHR was decreased to 53.85 % ±3.98% at 100 nmol/L PMA. Staurosporine enhanced the cardiomyocyte unload contractile function. At 200 nmol/L Saurosporine ,shortening amplitude of WKY increased to 163.63 %±4.53%, while that of 4-month and 10-month SHR increased to 180.82%±4.61% and 180.97%±4.59% separately. 6)The effects of PMA and Staurosporine on the duration and rate of cardiomyocyte unloaded contractile PMA prolonged WKY's TR90, increased shortening rate and decreased the relengthening rate. PMA decreased TPS of 4-month SHR, prolonged TR90 and relengthening rate. PMA decreased 10-month SHR's the rate of shortening and relengthening. Staurosporine decreased the rate of shortening and relengthening in 4-momth SHR.In a word, a valid adult rat cardiomyocyte isolation technique was established; the systolic pressure and cell area of SHR were detected; shortening amplitude-frequency relationship of hypertrophic cardiomyocyte...
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