| Project/Area Number |
59440024
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Jikei University School of Medicine |
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Principal Investigator |
SAKAI Toshio 東京慈恵会医科大学, 医, 教授 (20056435)
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| Project Period (FY) |
1984 – 1985
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| Project Status |
Completed (Fiscal Year 1985)
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| Budget Amount *help |
¥12,000,000 (Direct Cost: ¥12,000,000)
Fiscal Year 1985: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1984: ¥11,000,000 (Direct Cost: ¥11,000,000)
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| Keywords | Skeletal muscle fiber / intracellular Ca / rapid cooling contracture aequorin / エクオリン / プロカイン |
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| Research Abstract |
Contraction-relaxation cycle in skeletal muscle fiber is considered to be regulated by the change of [ <Ca^(2+)> ]i and we intended to clarify the relation between temporal and spatial changes of [ <Ca^(2+)> ]i and tension. For measurement of [ <Ca^(2+)> ]i, Ca sensitive photoprotein, aequorin was injected into a fiber and resultant light was detected by photomultiplier with tension. Tension was produced by electrical stimulation and rapid cooling which was applied to caffeine treated muscle fiber. [ <Ca^(2+)> ]i reached about 6-8 <micro> M and Ca binding sites in troponin and parvalbumin were nearly saturated by <Ca^(2+)> . On the other hand, low concentrations of caffeine raised [ <Ca^(2+)> ]i which was subthreshold for contraction, and subsequent rapid cooling produced contracture. Threshold [ <Ca^(2+)> ]i for development of rapid cooling contracture was 1.4 <micro> M and [ <Ca^(2+)> ]i reached 3.1 <micro> when contracture was fully activated. In rapid cooling contracture, three phase changes of [ <Ca^(2+)> ]i were observed and intracellular free <Ca^(2+)> was considered to distribute inhomogeneously. [ <Ca^(2+)> ]i increase by cafffine was inhibited by procaine, and rise of [ <Ca^(2+)> ]i was also producted by <K^+> and <NO(゛-_3)> , which was also known to be suppressed by procaine. These results raise a question on threshold [ <Ca^(2+)> ]i in Ca-induced Ca release mechanism. Spatial distribution of intracellular <Ca^(2+)> could be detected by aequorin and fura 2 and we are now ready for measurement.
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