|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1994 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1993 : ¥1,600,000 (Direct Cost : ¥1,600,000)
Ca^<2+> entry coupled to intracellular Ca^<2+> pool (ICP), which is called "capacitative Ca^<2+> entry", was investigated in rat glioma C6 cells, human leukemia Jurkat cells and cultured rat hepatocytes. In C6 cells, the sustained increase in cytosolic free Ca^<2+> concentration ([Ca^<2+>]_i)induced by bombesin and thapsigargin (TG), a microsomal Ca^<2+>-ATPase inhibitor, was abolished in the presence of tetrandrine, a receptor-operated Ca^<2+> channel (ROC) inhibitor. The pretreatment with pertussis toxin (IAP), phorbol ester, protein kinase C (C-kinase) inhibitor, tyrosine kinase inhibitor or cytoskeleton inhibitor did not affect [Ca^<2+>] _i induced by bombesin and TG.In Jurkat cells, at least two kinds of ICPs, both of which are IP_3-and lysophosphatic acid (LPA)-sensitive, existed and LPA sensitive-ICP did not relate to "capacitative Ca^<2+> entry." In cultured hepatocytes, TG did not cause Ca^<2+> oscillation. Ruthenium red inhibited Ca^<2+> oscillation induced by vasopressin but not [Ca^<2+>] _i induced by TG.
We suggest that IAP-sensitive GTP-binding protein, C-kinase, tyrosine kinase and cytoskeleton are not involved in the activation of "capacitative Ca^<2+> entry" and that "capacitativeCa^<2+> entry" does not relate to Ca^<2+> oscillation. Furthermore, there seems to exist two kinds of ICPs, one of which couples to "capacitative Ca^<2+> entry."