Winter C R, Baker R C
University of Mississippi Medical Center, Department of Pharmacology and Toxicology, Jackson 39216, USA.
Life Sci. 1995;57(21):1925-34. doi: 10.1016/0024-3205(95)02179-m.
The effects of L-glutamate, N-methyl-D-aspartate (NMDA), kainate (KA) and L-alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionate (AMPA) on intracellular Ca2+ oscillation frequency were studied in cultured rat myocardial cells. Ca2+ oscillations per minute were increased as compared to control by L-glutamate (100 microM) from 3.8 +/- 2.2 to 25.7 +/- 4.3 (p < 0.001) and the NMDA-receptor agonist, NMDA (100 microM), from 1.2 +/- 0.8 to 34.8 +/- 10.1 (p < 0.011). Increases over control frequency were also seen in response to the non-NMDA receptor agonists KA (100 microM) from 5.8 +/- 2.3 to 25.6 +/- 3.2 (p < 0.001) and AMPA (10 microM) from 3.8 +/- 1.2 to 13.3 +/- 1.8 (p < 0.001). The non-competitive NMDA receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK801) (10 microM), decreased the Ca2+ oscillation frequency induced by NMDA (100 microM from 36.8 +/- 12.2 to 7.2 +/- 7.2 (p < 0.05). (+/-)-2-Amino-7-phosphonoheptanoic acid (AP7), a competitive inhibitor at the NMDA receptor inhibited the increase in frequency induced by KA (100 microM) at all concentrations tested (0.1, 1.0, 10 and 100 microM). 6,7-Dinitroquinoxaline-2,3-dione (DNQX), a competitive inhibitor at non-NMDA receptors, also decreased the oscillation frequency elicited by KA (100 microM) from 35.4 +/- 9.4 to 28.2 +/- 9.8, 24.8 +/- 9.8 and 11 +/- 9.5 at concentrations of 0.1, 1.0 and 10 microM respectively. The peak amount of intracellular Ca2+ as expressed as the fluo 3 ratio, F/Frcst, was not increased by L-glutamate, NMDA or KA. These results suggest the presence of a novel glutamate receptor composed of both non-NMDA and NMDA subunits on cultured rat myocardial cells, and receptor stimulation leads to an increase in intracellular Ca2+ oscillation frequency.
在培养的大鼠心肌细胞中研究了L-谷氨酸、N-甲基-D-天冬氨酸（NMDA）、海人酸（KA）和L-α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）对细胞内Ca2+振荡频率的影响。与对照组相比，L-谷氨酸（100μM）使每分钟Ca2+振荡次数从3.8±2.2增加到25.7±4.3（p<0.001），NMDA受体激动剂NMDA（100μM）使振荡次数从1.2±0.8增加到34.8±10.1（p<0.011）。对非NMDA受体激动剂KA（100μM）的反应也观察到频率高于对照频率，从5.8±2.3增加到25.6±3.2（p<0.001），对AMPA（10μM）的反应从3.8±1.2增加到13.3±1.8（p<0.001）。非竞争性NMDA受体拮抗剂（+）-5-甲基-10,11-二氢-5H-二苯并[a,d]环庚烯-5,10-亚胺马来酸盐（MK801）（10μM）降低了NMDA（100μM）诱导的Ca2+振荡频率，从36.8±12.2降至7.2±7.2（p<0.05）。NMDA受体的竞争性抑制剂（±）-2-氨基-7-膦酰庚酸（AP7）在所有测试浓度（0.1、1.0、10和100μM）下均抑制KA（100μM）诱导的频率增加。非NMDA受体的竞争性抑制剂6,7-二硝基喹喔啉-2,3-二酮（DNQX）也降低了KA（100μM）引起的振荡频率，在0.1、1.0和10μM浓度下分别从35.4±9.4降至28.2±9.8、24.8±9.8和11±9.5。以荧光素3比率F/Frcst表示的细胞内Ca2+峰值量未因L-谷氨酸、NMDA或KA而增加。这些结果表明，在培养的大鼠心肌细胞上存在一种由非NMDA和NMDA亚基组成的新型谷氨酸受体，受体刺激导致细胞内Ca2+振荡频率增加。
