Age-related changes in transient outward potassium current of rat ventricular myocyte / 生理学报

The study aimed to investigate the age-related changes and drug reactions of transient outward potassium current (Ito) of ventricular myocytes. Twenty-eight Sprague Dawley rats were divided into young (3-5 months), adult (13-15 months) and aged (22-24 months) groups, and Ito currents of isolated myocytes from each group were recorded respectively by patch-clamp. The perfusion of 2.0 mmol/L 4-AP or 1.0 μmol/L isoproterenol was added respectively in each group, and the changes of Ito were observed. In comparison with young and adult groups, Ito densities of ventricular myocytes in aged group was significantly increased, the curve of steady-state activation of Ito shifted to the left, the close-state inactivation rate significantly decreased, and recovery rate from the steady-state inactivation became quicker. However, no significant changes could be detected for the Ito steady-state inactivation of ventricular myocytes in aged group. The similar responsiveness to 4-AP was observed in all three groups, but the responsiveness to isoproterenol was weaker in the aged group (55.9%) than in the other two groups (127.5% and 125.8%). In conclusion, the results show that Ito of rat ventricular myocyte of aging heart has increased current density and decreased response to isoproterenol.

Effect of neurotrophin p75 receptor activation on transmural dispersion repolarization in rabbits with myocardial infarction / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To elucidate the effect of neurotrophin p75 receptor (p75NTR)on transmural dispersion repolarization (TDR) of the layers of left ventricular myocytes in rabbits with myocardial infarction (MI).</p><p><b>METHODS</b>Forty Japanese rabbits were divided into four groups (n = 10): (1) Sham group, (2) Heald myocardial infarction (HMI) group, (3) p75 NTR activation group, (4) p75 NTR inhibition group. Cardiomyocytes were isolated with enzyme digestion and the currents were recorded by whole-cell patch-clamp technique.</p><p><b>RESULTS</b>Compared with those in the sham group, the duration of 90% action potential repolarization (APD90) and transmural dispersion repolarization of three layers of left ventricular myocytes were obviously raised (P < 0.05). But significant reduction was observed in p75NTR(-) group. Current densities of Ito and I(Ks, tail) in the p75NTR(+) group and HMI group were significantly reduced (P < 0.05), especially in mid myocytes. And no obvious changes were observed in p75NTR(-) group.</p><p><b>CONCLUSION</b>Activation of p75NTR(+) increases transmural dispersion repolarization, which may lead to the incidence of arrhythmia.</p>

Frequency- and state-dependent blockade of human ether-a-go-go-related gene K+ channel by arecoline hydrobromide / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The rapidly activating delayed rectifier potassium current (I(Kr)), whose pore-forming alpha subunit is encoded by the human ether-a-go-go-related gene (hERG), is a key contributor to the third phase of action potential repolarization. The aim of this study was to investigate the effect and mechanism of arecoline hydrobromide induced inhibition of hERG K(+) current (I(hERG)).</p><p><b>METHODS</b>Transient transfection of hERG channel cDNA plasmid pcDNA3.1 into the cultured HEK293 cells was performed using Lipofectamine. A standard whole-cell patch-clamp technique was used to record the I(hERG) before and after the exposure to arecoline.</p><p><b>RESULTS</b>Arecoline decreased the amplitude and the density of the I(hERG) in a concentration-dependent manner (IC(50) = 9.55 mmol/L). At test potential of +60 mV, the magnitude of I(hERG) tail at test pulse of -40 mV was reduced from (151.7 ± 6.2) pA/pF to (84.4 ± 7.6) pA/pF (P < 0.01, n = 20) and the magnitude of I(hERG) tail at test pulse of -110 mV was reduced from (-187.5 ± 9.8) pA/pF to (-97.6 ± 12.6) pA/pF (P < 0.01, n = 20). The blockade of arecoline in the open and inactivated state was significant in a state-dependent manner. The maximal blockade was achieved in the inactivated state. Studies of gating mechanism showed that the steady-state activation curve of I(hERG) was significantly negatively shifted by arecoline. Time constants of activation were shortened. Steady-state inactivation curve and time constants of fast inactivation were not significantly affected by arecoline. Furthermore, the inhibition of I(hERG) by arecoline was characterized markedly by a frequency-dependent manner from 0.03 to 1.00 Hz pulse.</p><p><b>CONCLUSION</b>Arecoline could potently block I(hERG) in both frequency and state-dependent manner.</p>

Study on residue analysis method of imidacloprid in Ephedrae sinica / 中国中药杂志

<p><b>OBJECTIVE</b>To establish residue analysis method of imidacloprid in Ephedra sinica by HPLC.</p><p><b>METHOD</b>Imidacloprid was extracted with dichloromethane, cleaned up with chromatography column, then separated on Spherisorb C18 column by using Methanol-water (20:80), detected at 270 nm.</p><p><b>RESULT AND CONCLUSION</b>The limit of detection (LOD) and limit quantification (LOQ) were 0.4 x 10(-9) g and 0.02 mg x kg(-1), mean recovery and related standard deviation (RSD) were 85.37%-90.65% and 2.23%-3.45%. It is concluded that the method could satisfy the pesticide residue analysis demands in sensitivity, accuracy and precision.</p>