Chou C L, Shirahata M
Department of Environmental Health Sciences, School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, MD 21205, USA.
Brain Res. 1996 Dec 2;742(1-2):34-42. doi: 10.1016/s0006-8993(96)00987-0.
The purpose of this study was to investigate if the oxygen-sensitive K channel is present in the carotid body cells of adult cats, and if all carotid body cells express the oxygen-sensitive K channel. A standard patch-clamp technique with a whole-cell configuration was applied to cultured carotid body cells from adult cats. The cells were continuously perfused with Krebs equilibrated with 5% CO2/air or 5% CO2/argon at room temperature. The results showed that electrophysiologically at least two types of cells existed in cultured cat carotid body cells. One type expressed the oxygen-sensitive K channel and the other expressed the oxygen-insensitive K channel. The oxygen-sensitive K channel was voltage-dependent with a threshold potential of -30 mV. No inactivation was observed during 40 ms of stimulation. The slope of the steady-state current-voltage curve was almost linear in the range from -30 mV to +50 mV. Hypoxia (pO2 = 25 mmHg) reversibly depressed the K current by 22%. The current was inhibited by 4-aminopyridine (10 mM) and tetraethylammonium (4-25 mM), but insensitive to charybdotoxin (100 nM). The oxygen-insensitive K channel showed similar characteristics to that of the oxygen-sensitive K channel in the threshold and the speed of activation, and the shape of I-V curve. The cat is the third species in which the oxygen-sensitive K channel was found in the carotid body. The sensitivity of K channels to oxygen may be a unique feature of chemosensory cells, but the properties of the oxygen-sensitive K channels are different among cats, rats, and rabbits.
本研究的目的是调查成年猫的颈动脉体细胞中是否存在氧敏感钾通道，以及所有颈动脉体细胞是否都表达氧敏感钾通道。采用标准的全细胞膜片钳技术对成年猫培养的颈动脉体细胞进行研究。在室温下，用含5%二氧化碳/空气或5%二氧化碳/氩气平衡的 Krebs 液持续灌注细胞。结果表明，在培养的猫颈动脉体细胞中，电生理上至少存在两种类型的细胞。一种类型表达氧敏感钾通道，另一种表达氧不敏感钾通道。氧敏感钾通道是电压依赖性的，阈值电位为 -30 mV。在40 ms的刺激过程中未观察到失活现象。稳态电流-电压曲线的斜率在 -30 mV至 +50 mV范围内几乎呈线性。低氧（pO2 = 25 mmHg）可使钾电流可逆性降低22%。该电流被4-氨基吡啶（10 mM）和四乙铵（4 - 25 mM）抑制，但对大蝎毒素（100 nM）不敏感。氧不敏感钾通道在阈值、激活速度和电流-电压曲线形状方面与氧敏感钾通道具有相似的特征。猫是在颈动脉体中发现氧敏感钾通道的第三个物种。钾通道对氧的敏感性可能是化学感受细胞的一个独特特征，但氧敏感钾通道的特性在猫、大鼠和兔子之间有所不同。
