| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1989: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
In the first year, we reported that trifluoperazine, a calmodulin antafonist, increased Ca^<2+>-sensitivity in Ca^<2+>-induced tension developed by skinned fibers from frog skeletal muscle. This effect is not due to the inhibition of calmodulin. Only the increase in Ca^<2+>-affinity of troponin C cannot be the explanation for it. In the second year, we found that calmodulin- antagonism and Ca^<2+>-sensitizing action are not parallel among other calmodulin antagonists, chlorpromazine, W-7 and melittin which are different in chemical structure, confirming the previous conclusion. During the course of the investigation, we realized that Ca^<2+>-induced tensions might dissociate from actomyosin-type ATPase activities. Then we planned in the last year to manage to determine simultaneously both activities with skinned fibers from rat or guinea-pig fast-twitch skeletal muscle. Interference by the sarcoplasmic reticulum ATPase activity; which was estimated to be 5% or less with mechanically skinned fibers, can be removed by treatment with 1% CHAPS. Using CHAPS-treated fibers at a sarcomere length of 2.5 mum, the ATPase-pCa curve were observed in a lower Ca^<2+> concentration range than the tension-pCa curve. At a longer sarcomere length of 3.0 mum, however, only the tension-pCa curve was shifted to a lower Ca^<2+> concentration range, resulting in little difference between tension and ATPase activities. Caffeine affected similarly both activities. To clarify the effects of other drugs, combination of flash- photolysis of caged-ATP and rapid quench by freezing technique are required.
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