Protein kinase C enhances the swelling-induced chloride current in human atrial myocytes / 华中科技大学学报（医学）（英德文版）

Swelling-activated chloride currents (ICl.swell) are thought to play a role in several physiologic and pathophysiologic processes and thus represent a target for therapeutic approaches. However, the mechanism of ICl.swell regulation remains unclear. In this study, we used the whole-cell patch-clamp technique to examine the role of protein kinase C (PKC) in the regulation of ICl.swell in human atrial myocytes. Atrial myocytes were isolated from the right atrial appendages of patients undergoing coronary artery bypass and enzymatically dissociated. ICl.swell was evoked in hypotonic solution and recorded using the whole-cell patch-clamp technique. The PKC agonist phorbol dibutyrate (PDBu) enhanced ICl.swell in a concentration-dependent manner, which was reversed in isotonic solution and by a chloride current inhibitor, 9-anthracenecarboxylicacid. Furthermore, the PKC inhibitor bis-indolylmaleimide attenuated the effect and 4α-PDBu, an inactive PDBu analog, had no effect on ICl.swell. These results, obtained using the whole-cell patch-clamp technique, demonstrate the ability of PKC to activate ICl,swell in human atrial myocytes. This observation was consistent with a previous study using a single-channel patch-clamp technique, but differed from some findings in other species.

Role of Stretch-Activated Channels in Stretch-Induced Changes of Electrical Activity in Rat Atrial Myocytes

We developed a cardiac cell model to explain the phenomenon of mechano-electric feedback (MEF), based on the experimental data with rat atrial myocytes. It incorporated the activity of ion channels, pumps, exchangers, and changes of intracellular ion concentration. Changes in membrane excitability and Ca2+ transients could then be calculated. In the model, the major ion channels responsible for the stretch-induced changes in electrical activity were the stretch-activated channels (SACs). The relationship between the extent of stretch and activation of SACs was formulated based on the experimental findings. Then, the effects of mechanical stretch on the electrical activity were reproduced. The shape of the action potential (AP) was significantly changed by stretch in the model simulation. The duration was decreased at initial fast phase of repolarization (AP duration at 20% repolarization level from 3.7 to 2.5 ms) and increased at late slow phase of repolarization (AP duration at 90% repolarization level from 62 to 178 ms). The resting potential was depolarized from -75 to -61 mV. This mathematical model of SACs may quantitatively predict changes in cardiomyocytes by mechanical stretch.

Effects of atrial fibrillation on expressions of connexin40 and connexin43 in atrial myocytes in rheumatic heart disease patients / 第三军医大学学报

6 months (n=12), control group, without AF (n=8). Atrial muscle samples of the left and right atrial appendage were cut off during heart valve replacement. Expressions of Cx40 and Cx43 were detected by immunoblotting and immunohistologic analyses. Results ①No obvious change of Cx43 and Cx40 in the left and right atrium of each patient in each group was measured. ②Compared with that in the control group, the level of Cx40 was decreased signficantly in GroupⅠ (P

The Effects of Immobilization Stress on the Ultrastructure of Rat Atrial Myocytes / 체질인류학회지

This study was performed to investigate the subcellular changes of rat atrial muscle cells by immobilization stress. Sprague -Dawley rats weighting 200 gm were immobilized in small round plastic tube for 2, 6, 12, and 24 hours respectively. The atrial tissue obtained from each animals were observed by transmission electron microscopes. In the heart of rat subjected 2 hours immobilization stress no significant morphological changes were found in electron microscopy, similarly as in control animal. After 6 and 12 hours immobilization stress, the following electron -microscopic changes of atrial myocytes were observed at the swelling of mitochondrial matrix with disturbance in cristea, focal loss of cytoplasmic matrix, vacuoles with myeline -like structure, apoptotic changes of myocytes, focal widening of intercalated disc interspace and lysis of myofibrils. After 24 hours immobilization stress, very small sized mitochondria, similarly as small sized secretory granules and various sized granules are observed in the perinuclear region of atrial myocytes. Atrial specific granules are moved centripetally toward the central region of the atrial myocytes after immobilization stress. Above results will be aid in understanding the structures of atrium with dual function of blood circulation and endocrine, and in research of modulation of secretory granules in atrial muscle cells.