Biological Research Laboratories, Sankyo Co., Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo, 140, Japan, Phone: (03) 3492-3131, Fax: (03) 3492-0207.
Platelets. 1993;4(2):91-5. doi: 10.3109/09537109309013202.
Ca(2+) and pH(i) were measured in unstimulated and thrombin-stimulated platelets from young (3 months) and aged (24 months) rats in the presence and absence of external Ca(2+). There was no difference in the basal level of Ca(2+) between young and aged rat platelets in the presence of external Ca(2+). On the other hand, thrombin-induced Ca(2+) mobilization was markedly increased in aged rat platelets compared to young rat platelets in the presence of external Ca(2+). This difference in Ca(2+) mobilization was more pronounced in the absence of external Ca(2+), suggesting that Ca(2+) release from intracellular storages was enhanced in aged rat platelets. In contrast to what was observed for Ca(2+), the basal level of pH(i) in aged rat platelets was higher than that in young rat platelets whereas thrombin-induced pH(i) increases (ΔpH) were similar in both groups in the presence and absence of external Ca(2+). These results indicate that age-associated changes occur in thrombin-induced Ca(2+) release from intracellular storages in rat platelets. These changes seem to be related to those in basal pH(i) levels.
[Ca2+]（i）和 pH（i）在有或没有外部 Ca2+的情况下，在年轻（3 个月）和年老（24 个月）大鼠的未刺激和凝血酶刺激血小板中进行了测量。在存在外部 Ca2+的情况下，年轻和年老大鼠血小板的基础[Ca2+]（i）水平没有差异。另一方面，与年轻大鼠血小板相比，在存在外部 Ca2+的情况下，凝血酶诱导的 Ca2+动员在年老大鼠血小板中明显增加。在不存在外部 Ca2+的情况下，这种 Ca2+动员的差异更为明显，表明年老大鼠血小板中细胞内储存的 Ca2+释放增强。与 Ca2+观察到的情况相反，在存在和不存在外部 Ca2+的情况下，年老大鼠血小板的基础 pH（i）水平高于年轻大鼠血小板，而两组的凝血酶诱导的 pH（i）增加（ΔpH）相似。这些结果表明，在大鼠血小板中，与年龄相关的变化发生在凝血酶诱导的细胞内储存的 Ca2+释放中。这些变化似乎与基础 pH（i）水平的变化有关。
