Menè P, Teti A, Pugliese F, Cinotti G A
Division of Nephrology, University of Rome, La Sapienza, Italy.
Kidney Int. 1994 Jul;46(1):122-8. doi: 10.1038/ki.1994.251.
Ca2+ influx is a major component of the response of cultured human mesangial cells (HMC) to vasoconstrictors. Activators of phospholipase C such as angiotensin II (Ang II) release Ca2+ from intracellular stores and enhance Ca2+ influx, which in turn is modulated by Na+/Ca2+ exchange. By microfluorometry we studied the mechanisms of Ca2+ entry in resting and stimulated fura-2-loaded monolayers or single HMC. Addition of 1 to 10 mM extracellular Ca2+ to cells equilibrated in Ca(2+)-free media resulted in a rapid, persistent elevation of free cytosolic Ca2+ ([Ca2+]i), from 52 +/- 5 to 113 +/- 18 and 226 +/- 37 nM, respectively. Ca2+ influx was blocked by lanthanum or chelation with EGTA, while it was only partially inhibited by voltage-operated Ca2+ channel (VOC) blockers, such as nifedipine or verapamil. The rise of [Ca2+]i at high external [Ca2+] was not due to a Ca(2+)-sensing mechanism with release of intracellular stored Ca2+, since it was prolonged, and it was not seen in cells maintained in normal 1.25 mM [Ca2+] media. Moreover, it was not abolished by prior depletion of Ca2+ stores with 0.5 microM thapsigargin or 5 microM ionomycin in Ca(2+)-free media, which transiently increased [Ca2+]i (to 281 +/- 39 and 380 +/- 51 nM, respectively). On the contrary, both agents markedly potentiated Ca2+ influx upon addition of 1 to 10 mM [Ca2+]e, (to a maximum of 686 +/- 111 and 633 +/- 150 nM, P < 0.05 vs. control).(ABSTRACT TRUNCATED AT 250 WORDS)
钙离子内流是培养的人系膜细胞（HMC）对血管收缩剂反应的主要组成部分。磷脂酶C激活剂如血管紧张素II（Ang II）从细胞内储存库释放钙离子并增强钙离子内流，而钙离子内流又受钠/钙交换调节。通过显微荧光测定法，我们研究了静息和刺激的负载fura-2的单层细胞或单个HMC中钙离子进入的机制。向在无钙培养基中平衡的细胞添加1至10 mM细胞外钙离子，导致游离胞质钙离子（[Ca2+]i）迅速、持续升高，分别从52±5 nM升至113±18 nM和226±37 nM。镧或与乙二醇双（2-氨基乙基醚）四乙酸（EGTA）螯合可阻断钙离子内流，而电压门控钙离子通道（VOC）阻滞剂如硝苯地平或维拉帕米仅部分抑制钙离子内流。高细胞外[Ca2+]时[Ca2+]i的升高并非由于钙离子传感机制释放细胞内储存的钙离子，因为这种升高是持续的，并且在维持于正常1.25 mM [Ca2+]培养基中的细胞中未观察到。此外，在无钙培养基中用0.5 microM毒胡萝卜素或5 microM离子霉素预先耗尽钙离子储存库并不能消除这种升高，毒胡萝卜素或离子霉素会使[Ca2+]i短暂升高（分别升至281±39 nM和380±51 nM）。相反，在添加1至10 mM [Ca2+]e后，这两种试剂均显著增强钙离子内流（最高可达686±111 nM和633±150 nM，与对照组相比P<0.05）。（摘要截断于250字）
