PROPERTIES OF THE LOW THRESHOLD CA CURRENT IN SINGLE FROG ATRIAL CARDIOMYOCYTES - A COMPARISON WITH THE HIGH THRESHOLD CA CURRENT
PROPERTIES OF THE LOW THRESHOLD CA CURRENT IN SINGLE FROG ATRIAL CARDIOMYOCYTES - A COMPARISON WITH THE HIGH THRESHOLD CA CURRENT
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DOI：
10.1085/jgp.100.3.519
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发表时间：
1992-09-01
影响因子：
3.8
通讯作者：
VASSORT, G
中科院分区：
文献类型：
--
作者：
ALVAREZ, JL;VASSORT, G
The properties of the low threshold Ca current (I(CaT)) in bullfrog (Rana catesbeiana) isolated atrial cardiomyocytes were studied using the whole-cell recording patch-clamp technique and compared with those of the high threshold Ca current (I(CaL)). In 91% of atrial cells we observed both I(CaT) and I(CaL) when collagenase and trypsin were used to dissociate the cells. But when pronase was used, only 30% of the cells exhibited I(CaT). I(CaT) was never found in ventricular cells. I(CaT) could be investigated more easily when I(CaL) was inhibited by Cd ions (50-mu-M). Its kinetics were unchanged by substituting Ba for Ca, or in the presence of high concentrations of Ba. Both I(CaT) and I(CaL) exhibited reduced inactivation after high depolarizing prepulses. I(CaT) was found to be sensitive to dihydropyridines: 1-mu-M nifedipine decreased this current while 1-mu-M BAY K 8644 increased it; this occurred without significant variations in the steady-state inactivation curve. I(CaT) was more sensitive than I(CaL) to alpha-1-adrenergic and P2-purinergic stimulations, while I(CaL) Was more sensitive to beta-adrenergic stimulation. Isoproterenol was still able to increase I(CaT) in the presence of high intracellular cAMP. Both currents were increased by 1-mu-M ouabain (although I(CaL) only transiently) and decreased by 10-mu-M ouabain. It is concluded that the two types of Ca channels can be observed in bullfrog atrial cells and that they are specifically altered by pharmacological agents and neuromediators. This may have implications for cardiac behavior.
