TNF-a对大鼠肾小球前小动脉平滑肌细胞Ca^(2+)内流的影响

Tumor necrosis factor-a effect on the influx of calcium rat glomerular afferent arteriole smooth muscle cells

目的:为探讨肿瘤坏死因子-a(TNF-a)对肾小球前小动脉平滑肌细胞Ca^(2+)内流的影响,以阐明TNF-a在肝肾综合征(HRS)发病中的作用。方法:通过对大鼠肾小球前小动脉平滑肌细胞(RASMC)的分离、培养,应用同位素方法检测在TNF-a作用下培养细胞的Ca^(2+)内流情况,研究在TNF-a作用下,蛋白激酶C(PKC)抑制剂对TNF-a诱导的RASMC Ca^(2+)内流作用的影响。结果:TNF-a增强RASMC的Ca^(2+)内流,作用时间长达60min,以后逐渐下降;Ca^(2+)通道阻断剂硝苯地平明显抑制了TNF-a促进Ca^(2+)内流的作用,硝苯地平添加组细胞内流的Ca^(2+)水平为2211.3±406.8cpm,未添加组为3326.2±315.2cpm,P<0.01;PKC抑制剂也明显抑制了TNF-a促进Ca^(2+)内流的作用。GFX添加组细胞内流的Ca^(2+)水平为2095.8±395.2cpm,未添加组为3326.4±315.2cpm,P<0.01。结论:TNF-a在HRS的发生中起到一定作用,其作用机制可能是通过促进肾小球前小动脉平滑肌细胞内Ca^(2+)水平增高而实现的。TNF-a可能是通过活化PKC后使在肾小球前小动脉平滑肌细胞膜上的Ca^(2+)通道开放,引起肾小球前小动脉平滑肌细胞内Ca^(2+)迅速上升,导致肾小球前小动脉平滑肌收缩,从而使肾血流量减少,肾小球滤过率下降,促使HRS发生。

AIM: To observe the effect of tumor necrosis factor (TNF-a) on influx of calcium of rat glomerular afferent arteriole smooth muscle cells (RASMC) and to illustrate the role of TNF-a in the mechanism of HRS. METHODS: The influx of calcium was measured in cultured RASMC treated with TNF-a and inhibitor of protein kinase C (PKC) by liquid scintillation counting. RESULTS: TNF-a increased calcium flux into RASMC and it lasted 60 minutes, then dropped. Nifedipine, an inhibitor of calcium channel, also inhibited the influx of calcium induced by TNF-a in RASMC. The level of calcium in RASMC treated with Nifedipine (2211.3±406.8cpm) was significantly lower than control (3326.2±315.2cpm, P<0.01). Bisindolylmaleimide (GFX), an inhibitor of PKC, inhibited obviously the effect of TNF-a of increasing the influx of calcium. The level of calcium in RASMC treated with GFX (2095.8±395.2cpm) was significantly lower than control (3326.4±315.2 cpm, P<0.01). CONCLUSIONS: It is possible that TNF-a plays a role in hepatorenal syndrome (HRS). The mechanism may be that TNF-a is involved in the influx of calcium in RASMC. TNF-a activates the PKC, as a modulator of intracellular calcium sensitivity, which makes the calcium channel open. This leads in turn to a subsequent the influx of calcium of RASMC and the contract of glomerular afferent arteriole that is a major determinant of blood flow in general and the kidney in particular. So, the diminution of renal blood flow and the decreasing of renal glomerular filter rate happened that result in HSR.