Latzkovits L, Torday C, Labourdette G, Pettmann B, Sensenbrenner M
Institute of Experimental Surgery, Medical School of Szeged, Hungary.
Neurochem Res. 1988 Sep;13(9):837-48. doi: 10.1007/BF00970751.
Primary cultures of rat astroglial cells were maintained in a serum-free medium. After 8-10 days of cultivation the cells were exposed to an astroglial growth factor (AGF2) for short periods (1-120 min). Subsequently, uptake of 22Na+ and 42K+ into control and AGF2-pretreated cells was studied. Assay of the Na+ and K+ values in the cells was also performed by atomic absorption spectrometry. Treatment of rat astroglial cells with AGF2 resulted in a significant increase of the uptake of both Na+ and K+ depending on the duration of the exposure period. To reach the maximum increase of cation uptake, 6-10 min and 30 min of AGF2 pretreatment were needed for Na+ and K+, respectively. Amiloride blocked this increase of Na+ and K+ uptake elicited by AGF2 pretreatment, but the control cells were amiloride resistant. Treatment with AGF2 increased the ouabain sensitivity of the K+ uptake as that: 10(-4) M ouabain inhibited K+ uptake of the AGF2-treated cells to the same degree as 5 X 10(-3) M ouabain with the control cells. The Na+ uptake of AGF2-treated cells, however, exhibited no relevant changes in the presence of ouabain. A significant part of the AGF2-induced K+ uptake could be inhibited by both ouabain and amiloride, but a ouabain-resistant and amiloride-sensitive component also was revealed. The furosemide sensitivity of both Na+ and K+ uptake into cultured astroglial cells was also significantly increased by AGF2. Our findings suggest that short-term exposure of cultured glial cells to AGF2 induces these very early ionic events: 1) The appearance of a relevant amiloride-sensitive Na+/H+ exchange, and as a consequence of increased Na+ entry into the cells, secondary activation of the ouabain-sensitive K+ uptake via the Na+,K+-pump. 2) A direct effect of AGF2 on the Na+,K+-pump assembly in the membrane, resulting in increased Na+ sensitivity of the inner pump sites and enhanced ouabain sensitivity of the external K+-binding sites. 3) An increase of ouabain-resistant but amiloride- or furosemide-sensitive Na+ and K+ uptake.
大鼠星形胶质细胞的原代培养物在无血清培养基中维持培养。培养8 - 10天后，将细胞短时间（1 - 120分钟）暴露于星形胶质细胞生长因子（AGF2）。随后，研究了对照细胞和经AGF2预处理的细胞对22Na+和42K+的摄取情况。还通过原子吸收光谱法对细胞中的Na+和K+值进行了测定。用AGF2处理大鼠星形胶质细胞会导致Na+和K+摄取量显著增加，这取决于暴露时间的长短。为使阳离子摄取量达到最大增加，Na+和K+分别需要6 - 10分钟和30分钟的AGF2预处理。氨氯吡咪可阻断AGF2预处理引起的Na+和K+摄取增加，但对照细胞对氨氯吡咪具有抗性。用AGF2处理会增加K+摄取对哇巴因的敏感性，具体表现为：10(-4)M哇巴因对经AGF2处理的细胞K+摄取的抑制程度与5×10(-3)M哇巴因对对照细胞的抑制程度相同。然而，在存在哇巴因的情况下，经AGF2处理的细胞的Na+摄取没有表现出相关变化。AGF2诱导的K+摄取的很大一部分可被哇巴因和氨氯吡咪抑制，但也发现了一个对哇巴因耐药但对氨氯吡咪敏感的成分。AGF2还显著增加了培养的星形胶质细胞对Na+和K+摄取的速尿敏感性。我们的研究结果表明，培养的胶质细胞短期暴露于AGF2会引发这些非常早期的离子事件：1）出现相关的氨氯吡咪敏感的Na+/H+交换，并且由于进入细胞的Na+增加，通过Na+,K+-泵继发激活对哇巴因敏感的K+摄取。2）AGF2对膜中Na+,K+-泵组件的直接作用，导致内部泵位点对Na+的敏感性增加以及外部K+结合位点对哇巴因的敏感性增强。3）对哇巴因耐药但对氨氯吡咪或速尿敏感的Na+和K+摄取增加。
