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概要

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• The relaxing effect of isoprenaline on [Na<SUP>+</SUP>] <SUB>o</SUB>-free induced contracture of the guinea-pig taenia coli was investigated in presence of phentolamine (10<SUP>-5</SUP>M), an alphareceptor blocking agent. This action of isoprenaline showed dose-dependency (ED 50: 10<SUP>-5</SUP>M) and was abolished completely by β-receptor blocking agent (propranolol, 10<SUP>-5</SUP>M). The effect of isoprenaline (10<SUP>-5</SUP>M) disappeared gradually during long exposure to [Na<SUP>+</SUP>] <SUB>o</SUB>-free solution and when short application of sodium ions to the perfusing solution, the effect of isoprenaline was restored. Pretreatment of [K<SUP>+</SUP>] <SUB>o</SUB>free solution or ouabain (10<SUP>-5</SUP>M) enhanced the effect of isoprenaline . The effect ofisoprenaline is inhibited by ouabain (10<SUP>-5</SUP>M) by about 50%. These observations strongly suggest that the inhibitory effect of isoprenaline may be mainly mediated through activation of Na-pump.However, direct activation of the drug on Na<SUP>+</SUP>-Ca<SUP>2+</SUP> exchange, Ca-pump, or Ca-uptake into cellular Ca store sites can not be ruled out.

• 日本平滑筋学会の論文

著者

• 那須 康典

  福岡大学医学部第一生理

• 那須 康典

  福岡大学医学部第一生理学教室

関連論文

• Electrical and mechanical interaction between circular and longitudinal muscle layers of the guinea-pig stomach.
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