| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2000: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1999: ¥1,600,000 (Direct Cost: ¥1,600,000)
|
|---|
| Research Abstract |
ATP is released by osmotic cell swelling in various cells. Osmotic cell swelling by hypotonic stress is known to be associated with a rise in intracellular calcium level ([Ca^<2+>]i). In this study, we examined the relationship between intracellular Ca^<2+> and ATP-release. Furthermore, we also examined the relationship between ATP-release and cell volume in order to know the physiological or pathophysiological role of ATP.
1. Relationship between intracellular Ca^<2+> and ATP-release
(1) Hypotonicity increased ATP-release and [Ca^<2+>]i in hypotonicity-dependent manner.
(2) BAPTA/AM (10 μM), a membrane permeable Ca^<2+> chelator, completely abolished increased [Ca^<2+>]i and ATP-release in hypotonicity.
(3) In the absence of extracellular Ca^<2+>, hypotonicity significantly increased [Ca^<2+>]i, but the extent of the increase was smaller than that in its presence, while the removal of extracellular Ca^<2+> also markedly enhanced ATP-release.
(4) Extracellular Ca^<2+> at higher concentratio
… More
n than normal potentiated the hypotonicity-induced increase in [Ca^<2+>]i, but did not increase ATP-release.
2. Relationship between cell volume and ATP-release
(1) Hypotonicity increased [Ca^<2+>]i and cell volume. The hypotonicity-induced increase in [Ca^<2+>]i was prevented by PPADS (a P2 purinoceptor antagonist), U-73122 (a phospholipase C inhibitor) and thapsigargin (a Ca^<2+> pump inhibitor).
(2) However, the hypotonicity-induced increase in the cell volume was potentiated by PPADS, U-73122 and thapsigargin.
(3) 2-MethylthioATP (P2-purinoceptor agonist) decreased the cell volume while increasing [Ca^<2+>]. Both actions of 2-methylthioATP were blocked by PPADS, U-73122 and by thapsigargin. From these findings, it was suggested hat the release of ATP induced by hypotonicity may be coupled with a specific localized intracellular Ca^<2+> and suppressively regulated by extracellular Ca^<2+>. Further, the present study suggests that ATP, which is released by hypotonicity, may participate in the RVD as a substantial regulator or initiator via P2 purinoceptor-induced increase in [Ca^<2+>]i. Less
|
