内钙动员调控凝血酶诱导的血小板Na^＋／H^＋交换

目的：研究凝血酶诱导的血小板活化中细胞内钙动员和Ｎａ＾＋／Ｈ＾＋交换的关系。方法Ｆｕｒａ－２负载测［Ｃａ＾２］ｉ和ＢＣＥＣＦ负载测ｐＨｉ。结果：凝血酶０．１ＩＵ·Ｌ＾－１引起［Ｃａ＾２＋］ｉ和ｐＨｉ，［Ｃａ＾２］ｉ增加先于ｐＨｉ增加。在无钠溶液中，Ｎａ＾＋／Ｈ＾＋交换被抑制而［Ｃａ＾２］ｉ增加不受影响；用尼日利亚菌素（１ｍｇ·Ｌ＾－１）使胞内酸化可抑制［Ｃａ＾２＋］ｉ增加，用依他酸（ＢＧＴＡ）阻断

Mobilization of intracellular Ca2+ modulates activation of Na+/H+ exchange in thrombin-stimulated platelets.

AIM: To study the relationship between intracellular calcium translocation and activation of Na+/H+ exchange in thrombin-stimulated platelets. METHODS: Intracellular Ca2+ (Ca2+]i) and pH (pHi) were measured by a dual wavelength fluorophotometer with Fura-2 and pH-sensitive probe BCECF. RESULTS: Thrombin 0.1 IU.L-1 elicited an increase in platelet Ca2+]i and pHi, the maximal increase in Ca2+]i occurred earlier than the rise in pHi. In Na(+)-free buffers, the Na+/H+ exchange was markedly suppressed without affecting the elevation of Ca2+]i; while intracellular acidification with nigericin 1 mg.L-1 inhibited the increment of Ca2+]i. Blockade of Ca(2+)-influx with egtazic acid (EGTA) did not affect cytosolic alkalinization. Depletion of intracellular Ca2+ store with ionomycin in the presence of EGTA, no increment in pHi was observed, the basal value of pHi was even more acidic, this response of pHi to thrombin was rehabilitated after refilling of intracellular Ca2+ store with extracellular Ca2+ 1 mmol.L-1. CONCLUSION: Intracellular Ca2+ mobilization modulated activation of Na+/H+ exchange, which required an effective increment of Ca2+]i.