Endurance training attenuates the bioenergetics alterations of rat skeletal muscle mitochondria submitted to acute hypoxia: role of ROS and UCP3 / 生理学报

The physiological significance of skeletal muscle mitochondrial uncoupling protein 3 (UCP3) in hypoxia is elusive. In the current study, UCP3 mRNA and protein expressions were investigated along with mitochondrial respiratory function, reactive oxygen species (ROS) generation, as well as manganese superoxide dismutase (MnSOD) expression in rat skeletal muscle with or without endurance training after an acute and severe hypobaric hypoxia exposure for different time. Acute hypoxia induced a series of impairments in skeletal muscle mitochondrial bioenergetics. In untrained rats, UCP3 protein content increased by 60% above resting level at 4 h hypoxia, whereas MnSOD protein content and activity were unaltered. UCP3 upregulation increased mitochondrial uncoupling respiration thus reducing O2(.-) generation, but inevitably decreased ATP production. Training decreased acute hypoxia-induced upregulation of UCP3 protein (67% vs 42%) in rat skeletal muscle. ROS production in trained rats also showed a dramatic decrease at 2 h, 4 h and 6 h, respectively, compared with that in untrained rats. MnSOD protein contents and activities were significantly (50% and 34%) higher in trained than those in untrained rats. Training adaptation of MnSOD may enhance the mitochondrial tolerance to ROS production, and reduce UCP3 activation during severe hypoxia, thus maintaining the efficiency of oxidative phosphorylation. In trained rats, mitochondrial respiratory control (RCR) and P/O ratios were maintained relatively constant despite severe hypoxia, whereas in untrained rats RCR and P/O ratios were significantly decreased. These results indicate that (1) UCP3 mRNA and protein expression in rat skeletal muscle are upregulated during acute and severe hypobaric hypoxia, which may reduce the increased cross-membrane potential (Deltapsi) and thus ROS production; (2) Endurance training can blunt hypoxia-induced UCP3 upregulation, and improve mitochondrial efficiency of oxidative phosphorylation due to increased removal of ROS.

Effect of yiqi huoxue recipe on cardiac function and ultrastructure in regression of pressure overload-induced myocardial hypertrophy in rats / 中国结合医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of Yiqi Huoxue Recipe (YHR) on the cardiac function and ultrastructure during the regression of myocardial hypertrophy induced by pressure overload in rats.</p><p><b>METHODS</b>The model of myocardial hypertrophy was established by abdominal aortic banding. Eighty male Wistar rats were divided into six groups, the normal control group I (n=20), the normal control group II (n=12), the hypertension model group I (n=12), the hypertension model group II (n=12), the YHR group (n=12) and the Captopril group (n=12). The observation was carried out in the normal control group I and the hypertension model group I after 4 weeks of modeling, and the other four groups were observed after 16 weeks of modeling (12 weeks of administration). The cardiac function was measured with a multichannel biological signal analysis system, and the myocardium ultrastructure was observed by a transmission electron microscope.</p><p><b>RESULTS</b>(1) Compared with the normal control group I, the systolic blood pressure and cardiac coefficient (left ventricular weight/body weight) in the model I group was higher (P<0.05, P<0.01). (2) In the YHR group, cardiac coefficient and -dp/dt(max) were lower, left ventricular systolic pressure and +dp/dt(min) were higher when compared with the model group II and the Captopril group (P<0.05 or P<0.01). In the Captopril group, only cardiac coefficient was lower when compared with the mode group II (P<0.05). (3) Compared with the normal control group II, +dp/dt(max) was higher (P<0.01) -dp/dt(max) and isovolumetric contraction time (ICT) was lower (P<0.05, P<0.01) in both the YHR group and the Captopril group. (4) Results of the myocardium ultrastructure showed edema under myocardium plasmalemma, enlarged sarcoplasmic reticulum and T tube, and significantly enlarged intercalated disc of the cardiac muscle in the model groups. In the Captopril group, the extension of sarcoplasmic reticulum and T tube as well as the pathological changes of intercalated disc were lighter, with slight edema under the myocardium plasmalemma. In the YHR group, the expansion of the sarcoplasmic reticulum was less than in the Captopril group, part of the pathological changes of intercalated discs was slightly more severe than that in the Captopril group, the dissolution of nuclear chromatin was not found, which was similar to that of the Captopril group, and no injury of the nucleus was found, either.</p><p><b>CONCLUSION</b>YHR could reverse myocardial hypertrophy in rats with abdominal aortic banding and improve the systolic and diastolic function of the left ventricle. The ultrastructure of the myocardium such as arcoplasmic reticulum, intercalated disc, and cell nucleus in abdominal aortic banding rats could be partly reversed by the recipe.</p>

Responses of regional vascular beds to local injection of genistein in rats / 生理学报

The effects of local injection of genistein on femoral, renal, and mesenteric vascular beds were investigated respectively by constant flow perfusion method in 72 anaesthetized rats. The results are as follows: (1) genistein (0.4, 0.8, 1.2 mg/kg) decreased the perfusion pressure (PP) of femoral vascular bed in a dose-dependent manner. The effect of genistein (0.8 mg/kg) was partially inhibited by L-NAME, or by sodium orthovanadate (50 microg/kg), a potent inhibitor of protein tyrosine phosphatase; (2) genistein also decreased the PP of renal vascular bed in a dose-dependent manner and the effect of genistein was completely inhibited by pretreatment with sodium orthovanadate, but unaffected by L-NAME; and (3) genistein decreased the PP of mesenteric vascular bed in a dose-dependent manner, an effect which was partially inhibited by sodium orthovanadate, but unaffected by L-NAME. From the results obtained, it is concluded that genistein can decrease the vascular tone in the femoral, renal, and mesenteric vascular beds with the underlying mechanism that involves tyrosine kinase inhibition, while in femoral arterial beds, it also involves NO release.

Phytoestrogen genistein inhibits carotid sinus baroreflex in anesthetized male rats / 生理学报

The purpose of this study was to determine the effect of phytoestrogen genistein (GST) on carotid sinus baroreflex in 30 anesthetized male rats by perfusing the isolated carotid sinus in vivo. The results obtained are as follows. (1) By perfusion with GST (50 micromol/L), the functional curve of baroreflex was shifted to the right and upward, with a peak slope (PS) decrease from 0.36+/-0.01 to 0.23+/-0.01 (P<0.001) and a reflex decrease (RD) in mean arterial pressure from 39.75+/-1.58 to 27.00+/-0.60 mmHg (P<0.001), while the threshold pressure (TP) and saturation pressure (SP) were significantly increased from 65.63+/-2.1 to 82.05+/-1.95 mmHg (P<0.001) and from 192.23+/-3.90 to 215.76+/-3.75 mmHg (P<0.001), respectively. Among the functional parameters of carotid baroreflex, the changes in RD, PS and TP were dose-dependent. (2) Pretreatment with Bay K 8644 (500 nmol/L), an agonist of calcium channels, could completely abolish the inhibitory effect of GST on carotid baroreflex. (3) Preperfusion with an inhibitor of NO synthase, L-NAME (100 micromol/L), did not affect the inhibitory effect of GST. It is proposed that the inhibitory action of GST on carotid baroreflex may be mediated by the inhibition of Ca(2+) channel of vascular smooth muscle, but not by NO release from endothelium.

Effect of agmatine on intracellular free calcium concentration in isolated rat ventricular myocytes / 生理学报

The present study was to investigate the effects of agmatine (Agm) on free intracellular calcium concentration ([Ca(2+)]( i )) of isolated rat ventricular myocytes. [Ca(2+)]( i ) was measured by confocal microscopy in single rat ventricular myocytes which were dissociated by enzymatic dissociation method and loaded with Fluo 3-AM. The changes in [Ca(2+)]( i ) were represented by fluorescence intensity (FI) or relative fluorescence intensity (F/F(0)%). The results showed that the control level of FI value of single rat ventricular myocytes was 128.8+/-13.8 and 119.6+/-13.6 in the presence of normal Tyrode's solution containing Ca(2+) 1.0 mmol/L and Ca(2+)-free Tyrode's solution, respectively. There was no difference between these two groups (P>0.05). Agm 0.1, 1, and 10 mmol/L significantly reduced the [Ca(2+)]( i ) in both extracellular solutions in a concentration-dependent manner. The similar effect of Agm on [Ca(2+)]( i ) was also observed in the presence of EGTA 3 mmol/L. KCl 60 mmol/L, PE 30 micromol/L, and Bay-K-8644 10 micromol/L, all these substances induced [Ca(2+)]( i ) elevations in ventricular myocytes. Agm (0.1, 1, and 10 mmol/L) markedly inhibited the increase in [Ca(2+)]( i ) induced by KCl, phenylephrine (PE), and Bay-K-8644. When Ca(2+) waves were produced by increasing extracellular Ca(2+) concentration from 1 to 10 mmol/L, 1 mmol/L Agm could block the propagating waves of elevated [Ca(2+)]( i ), and reduce the velocity and duration of propagating waves. These results suggest that Agm possesses an inhibitory effects on [Ca(2+)]( i ) via blocking voltage-dependent Ca(2+) channel, and possibly by alleviating calcium release from SR in single isolated rat ventricular myocytes.