1992 Fiscal Year Final Research Report Summary
Transmembrane Cl^- Movement in Cardiac Cells and Its Pathophysiological Significance
| Project/Area Number |
03670086
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
General pharmacology
|
|---|
| Research Institution | School of Medicine, Chiba University (1992)
Hokkaido University (1991) |
|---|
Principal Investigator |
NAKAYA Haruaki M.D. Department of Pharmacology School of Medicine, Chiba University Professor, 医学部 (60113594)
|
|---|
| Project Period (FY) |
1991 – 1992
|
| Keywords | Cl^- Channel / Cardiac Cells / Hypotonic Swelling / Depolarization of the Resting Membrane / beta-Adrenergic Stimulation / Cl^- Channel Blockers / Intracellular Cl^- Activity / Intracellular K^+ Activity |
|---|
| Research Abstract |
Electrophysiological experiments using ion-selective electrodes were conducted to determine whether cell swelling activates Cl^- current and whether the Cl^- current is different from that activated by beta-adrenergic stimulation. When ventricular myocytes isolated from guinea-pig heart were exposed to hyposmotic solution (67 % osmolality) for 5 min, cell width, cell length and calculated cell volume were increased by 9.6*1.4 %, 1.0*0.2 %and 21.6*3.3 %, respectively. The change in size was reversible and returned to the control level with switching back to the isosmotic solution. In isolated guinea-pig papillary muscles, 10-min superfusion of the hyposmotic solution (67% osmolality with constant K^+ concentration) produced decreases in action potential duration and resting membrane potential. In quiescent preparations the hyposmotic solution depolarized the resting membrane by 11.5*0.4 mV, which was significantly inhibited by 4, 4'- diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS, 1 mM) and 4- acetoamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS, 1 mM) but not by anthracene-9-carboxylic acid (9AC, 1 mM). In contrast with the membrane depolarization induced by hypotonic stress, the isoproterenol-induced membrane depolarization from -91.1*1.4 mV to -82.1*1.8 mV and decrease in intracellular Cl^- activity (a^iCl) from 32.1*7.8 mM to 23.1*6.0 mM was effectively inhibited by 1 mM 9AC but not by 1 mM DIDS. In guinea-pig papillary muscles superfusion of the hyposmotic solution decreased a^iCl by 46*5 %, which was significantly greater than the decrease in intracellular K^+ activity (26*3 %). These results suggest that the cell swelling induced by hyposmotic solution may activate DIDS- and SITS-sensitive Cl^- channel, resulting in a depolarization of the resting membrane. The Cl^- channel may be different from that activated by beta-adrenergic stimulation.
|
