ABSTRACT
Effect of strophanthidin (Str) on intracellular calcium concentration ([Ca2+]i) was investigated on isolated ventricular myocytes of guinea pig. Single ventricular myocytes were obtained by enzymatic dissociation technique. Fluorescent signal of [Ca2+]i was detected with confocal microscopy after incubation of cardiomycytes in Tyrode's solution with Fluo3-AM. The result showed that Str increased [Ca2+]i in a concentration-dependent manner. The ventricular myocytes began to round-up into a contracture state once the peak level of [Ca2+]i was achieved in the presence of Str (10 μmol·L-1), but remained no change in the presence of Str (1 and 100 nmol·L-1). Tetrodotoxin (TTX), nisodipine, and high concentration of extracellular Ca2+ changed the response of cardiomycytes to Str (1 and 100 nmol·L-1), but had no obvious effects on the action of Str (10 μmol·L-1). The elevation of [Ca2+]i caused by Str at all of the detected concentrations was partially antagonized by rynodine (10 μmol·L-1) or the removal of Ca2+ from Tyrode's solution. In Na+, K+-free Tyrode's solution, the response of cardiomycytes in [Ca2+]i elevation to Str (10 μmol·L-1) was attenuated, while remained no change to Str (1 and 100 nmol·L-1). TTX, nisodipine, and high concentration of extracellular Ca2+ changed the response of cardiomycytes to Str at all of the detected concentrations in Na+, K+-free Tyrode's solution. The study suggests that the elevation of [Ca2+]i by Str at the low (nomomolar) concentrations is partially mediated by the extracellular calcium influx through Ca2+ channel or a "slip mode conductance" of TTX sensitive Na+ channel. While the effect of Str at high (micromolar) concentrations was mainly due to the inhibition of Na+, K+-ATPase. Directly triggering the release of intracellular Ca2+ from sarcoplasmic reticulum (SR) by Str may be also involved in the mechanism of [Ca2+]i elevation.
ABSTRACT
Objective To study the inhibitory effect of valdecoxib on Lewis tumor and the potential relationship with cyclooxygenase-2(COX-2).Methods HE staining was used to observe lymphocyte infiltration in tumor tissue and the cell structure of the stomach and colon.Western blotting was used to detect the expression of COX-2 in tumor tissue.PGE_2 ELISA kit was used to detect the content of PGE_2 in tumor tissue.Results ① Valdecoxib inhibited the growth of the tumor,and the survival rate was increased.②There was lymphocyte infiltration in treatment group and the content of PGE_2 was decreased.③Valdecoxib did not affect cell structure of stomach and colon,bleeding and clotting time.Conclusion Valdecoxib inhibits the growth of the Lewis tumor and enhances the survival rate.The effect of valdecoxib is related to the inhibition of COX-2.
ABSTRACT
Aim To develop the animal model of guinea pig chronic heart failure and detect effects of chronic heart failure on contractile/diastolic function and calcium transient in guinea pig ventricular myocytes by video-based motion edge-detection system simultaneously.Methods The chronic congestive heart failure(CHF) model was produced in guinea pig by a procedure that descenting aorta was constricted.The contrasting indexes in 8 weeks include: with or without dyspnea,hemodynamics,the mass ratio of left ventricle to body,the mass ratio of lung to body,and the width of left ventricle.Left ventricular myocytes were enzymatically isolated.Then the contractile and calcium transient of a single cell from both normal and failure hearts were assessed in guinea pigs by a video-based motion edge-detection system simultaneously.Results The models with dyspnea showed striking increasing in left ventricular systolic pressure and left ventricular end diastolic pressure,as well as the mass ratio of left ventricle to body,the mass ratio of lung to body and the width of left ventricular hypertrophy.The left ventricular pressure maximal rising and declining velocity significantly decreased.Compared with normal cells,the value of shorting,the contractile and diastolic velocity of myocytes decreased significantly.The diastolic calcium increased,the extent of calcium transient[FL(2K2] decreased and the time to 50% diastolic calcium lengthen.But systolic calcium,the time to peak calcium were unchanged.Conclusions The dyspnea is a important parameter for evaluating the animal CHF model of guinea pig formed by constricting the descending aortas of guinea pigs after 8 weeks.The chronic heart failure may decrease contractile and calcium transient extent in ventricular myocytes detected by video-based motion edge-detection system simultaneously,which might be helpful for the further studying the mechanism of the development of CHF.
ABSTRACT
Aim To investigate the changes of Na~+,K~+-ATPase activity and ? isoforms in rat neurons suffered from global ischemia.Methods The BCAL rat was induced by bilateral carotid artery ligation.The contents of H_2O,Na~+ and K~+ in brain tissue were detected.The method of spectrophotometry was applied to measure the activities of Na~+,K~+-ATPase.With immunohistochemical assay,the expression of the Na~+,K~+-ATPase ?_1,?_2,or ?_3 isoform was detected in neurons of rat hippocampus and cortex following ischemia.Results In the BCAL rats,the contents of H_2O and Na~+ were increased while the content of K~+ and the activity of Na~+,K~+-ATPase were decreased.The ?_1,?_2 or ?_3 isoform of Na~+,K~+-ATPase distributed in a tissue-specific fashion in neurons of hippocampus and cortex,in which ?_1 and ?_3 were abundant and ?_3 was more than ?_1,but ?_2 was much less.In BCAL rat,?_1 and ?_3 isoforms were significantly decreased in hippocampus and cortex neurons.Conclusion These results suggest that the changes of Na~+,K~+-ATPase ?_1 and ?_3 isoforms may be involved in the global cerebral ischemia
ABSTRACT
Aim To observe effects of hypertension on contractile/diastolic function and calcium transient in rats ventricular myocytes. Methods The model of one-kidney-one-clip (1k1c) hypertensive rat was pre-pared by partially ligating the left renal artery and removing the right kidney. Left ventricular myocytes were enzymatically isolated. Then the contraction and calcium transient of a single cell from both normal and renovascular hypertensive rats were observed by a video-based motion edge-detection system simultaneously. Effects of calcium in various concentrations on contractile/diastolic function and calcium transient in ventricular myocytes from renovascular hypertensive rats were assessed in the same way. Results Compared with normal cardiac myocytes, the shorting amplitude and the contractile and diastolic velocity were increased significantly in 1k1c hypertensive rat cardiac myocytes. However their intracellular calcium in contractile and diastolic periods, the extent of calcium transient and the parameters of intracellular calcium dynamics were unchanged. But the extracellular calcium of different concentrations could shift the Fura-2 fluorescence ratio-cell shorting amplitude curve from hypertension rat myocytes to the left compared with that from normal rats. Conclusions The hypertension increases the contractility of rat cardiac myocytes, which is due to raising their sensitivity to calcium.