目的：研究小檗碱（Ber）对豚鼠心室细胞钾通道和动作电位作用，以及在蛙卵中表达的人的HERG通道的作用。方法：酶解方法分离单个心肌细胞，采用全细胞膜片箝方法记录钾离子电流及动作电位，基因箝技术研究HERG通道电流。结果：Ber可显著延长动作电位时程，并呈剂量依赖性。Ber 100μmo1/L使APD90由对照的 （450±48）ms 延长至（888±90）ms (n=6，P<0.01)。Ber对Ik1及Ik呈剂量依赖性抑制作用。Ber 100μmo1/L对Ik1的抑制率达65%±7%（n=6,P<0.01）。Ber 50 μmo1/L对Ik的抑制率达57%±6%；对Iktail的抑制率达53%±6%，Ber对Ik作用呈现电压依赖性。Ber对在硅卵中表达的HERG通道具有很强的阻断作用，IC50为75μmo1/L，此阻断作用也呈电压依赖性。结论：Ber可使动作电位时程明显延长，对Ik1及Ik具有阻断作用。Ber可显著抑制HERG通道。Ber抗心律失常的机制与其抑制Ik1、Ik及HERG通道密切相关。

Dopamine receptors exist in many tissues, including rat cardiac tissue. However, the physiological importance ofdopamine receptors in the homeostatic regulation of cardiac function is unclear. In this study, a model of ischaemia/reperfusion was established by culturing primary neonatal rat cardiomyocytes in ischaemia-mimetic solution for 2 hr, followedby incubation in normal culture medium for 24 hr. Lactate dehydrogenase activity, superoxide dismutase activity andmalondialdehyde content were determined colorimetrically with a spectrophotometer. Apoptotic cell death was assayed by3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, terminal deoxynucleotidyl transferase-mediateddUTP-biotin nick end labelling staining and flow cytometry, and morphological alterations were observed with transmissionelectron microscopy. The intracellular free calcium concentration ([Ca2+]i) was measured by confocal laser scanningmicroscopy. Finally, the expression of dopamine receptor 1 (DR1), caspase-3, -8 and -9, Fas, Fas ligand and Bcl-2 and therelease of cytochromecwere analysed by Western blot. The results showed that DR1 expression was increased markedlyduring ischaemia/reperfusion. Treatment with 10M SKF-38393 (DR1 agonist) significantly increased lactate dehydrogenaseactivity, decreased superoxide dismutase activity and increased malondialdehyde content in the culture medium. The DR1agonist promoted the release of cytochromec, accumulation of [Ca2+]i, and apoptosis induced by ischaemia/reperfusion.Furthermore, SKF-38393 up-regulated the expression of caspase-3, -8 and -9, Fas and Fas ligand, and down-regulatedBcl-2 expression. In contrast, 10M SCH-23390 (DR1 antagonist) had no significant effects on the above indicators. Inconclusion, DR1 activation is involved in the apoptosis of cultured neonatal rat cardiomyocytes in simulated ischaemia/reperfusion through the mitochondrial and death receptor pathways.

The calcium-sensing receptor (CaR) is a G protein-coupled receptor. The CaR stimulation elicits phospholipaseC-mediated inositol triphosphate formation, leading to an elevation in the level of intracellular calcium released from endoplasmicreticulum (ER). Depletion of ER Ca2+ leads to ER stress, which is thought to induce apoptosis. Intracellular calciumoverload-induced apoptosis in cardiac myocytes during hypoxia–reoxygenation (H ?Re) has been demonstrated. However, thelinks between CaR, ER stress and apoptosis during H?Re are unclear. This study hypothesized that the CaR could induceapoptosis in neonatal rat cardiomyocytes during H?Re via the ER stress pathway. Neonatal rat cardiomyocytes were subjectedto 3 hr of hypoxia, followed by 6 hr of reoxygenation. CaR expression was elevated and the number of apoptotic cells wassignificantly increased, as shown by transferase-mediated dUTP nick end-labelling, with exposure to CaCl2, a CaR activator,during H?Re. The intracellular calcium concentration was significantly elevated and the Ca2+ concentration in the ER wasdramatically decreased during H?Re with CaCl2; both intracellular and ER calcium concentrations were detected by laserconfocal microscopy. Expression of GRP78 (glucose-regulated protein 78), the cleavage products of ATF6 (activating transcriptionfactor 6), phospho-PERK [pancreatic ER kinase (PKR)-like ER kinase], the activated fragments of caspase-12, andphospho-JNK (c-Jun NH2-terminal kinase) were increased following exposure to CaCl2 during H?Re. Our results confirmedthat the activated CaR can induce cardiomyocyte apoptosis via ER stress-associated apoptotic pathways during H? Re.

采用全细胞电压钳技术, 以确定青蒿素对分离的豚鼠心室肌细胞和狗的浦肯野纤维钾离子电流的影响. 在豚鼠心室肌细胞, 青蒿素呈浓度依赖关系显著降低内向整流钾电流(IK1, 膜电位为- 100mV 时, IC50为(7. 2±0. 8) Lmol·L-1), 且这种抑制作用不呈现频率依赖性. 50 Lmol·L21的青蒿素降低延迟整流钾电流(I K) : 时间依赖性外向钾电流(IKstep) 在膜电位为+ 40 mV 时减少(38±10)%. 尾电流步阶分析提示, IK 的快组分(IKr) 和慢组分(I Ks)均被抑制. 在犬浦肯野纤维, 青蒿素明显抑制瞬时外向钾电流(Ito), IC50为(4. 2±0. 3) Lmol·L-1. 实验结果表明, 青蒿素以相似效率抑制I K1, I to 和I K,其抗心律失常作用可能与抑制I K1, I to, I Kr和I Ks有关。

This study was focused on investigating the involvement of polyamine metabolism in the myocardial ischemia-reperfusion injury (MIRI)in an in vivo rat model. A branch of the descending left coronary artery was occluded for 30 min followed by 2 h, 6 h, 12 h, and 24 hreperfusion. Then the expression of spermidine/spermine N1-acetyltransferase (SSAT) and ornithine decarboxylase (ODC) and theconcentrations of polyamines were assessed. It was found that the expression of SSAT and ODC were upregulated after reperfusion and theconcentrations of spermidine and spermine were significantly decreased, while putrescine concentration was significantly increased. Theresults suggest that MIRI may cause disturbance of polyamine metabolism, and it may play a critical role in MIRI