• 作者： 林正一; 林彩珠; 王長君
• 作者服務機構： 國防醫學院藥理學系; 國立臺灣海洋學院水產養殖學系; 國防醫學院生物形態學系
• 中文摘要： 本實驗研究河豚毒 (TTX) 去氧葡萄糖 (2-DG) 及丙酮酸鈉對離體狗心 Purkinje 纖維動作電位及收縮期間的影響
  ，以探討心室傳導組織動作電位平原期 (Plateau) 較長，收縮舒張週期較短的生理機轉。 TTX (1 gm/m ) 顯?縮短
  (-43％) Purkinje 纖維的動作電位期間，並抑制其收縮力 (-76％)；同劑量 TTX 在心室肌作用不顯?。在低鈉溶液
  中， Purkinje 纖維動作電位期間亦縮短，其平原期正值減小，但收縮力顯?增加。 lOmM 2-DG 在 40分鐘內抑制
  收縮力 44％ 減短動作電位期間 20％ ，但延長收縮期間 22％ ，在缺氧的 Tyrode 氏灌注液中， Purkinje 纖維收縮力
  亦減弱，唯收縮期間減短，丙酮酸鈉 (1OmM) 加速 Purkinje 纖維再極化，並顯?延長其收縮期間；在　TTX　處理後，
  丙酮酸鈉延長平原期時間，並升高平原期電位。電子鏡檢查發現　Purkinje　纖維粒線體較心室肌細胞小而細，以上結果
  顯示：(一)透過細胞膜的 Na influx 對狗心 Purkinje 纖維動作電位平原期的維持比 Ca influx 重要；(二) Purkinje纖維
  能量來源偏重醣解，由於心臟細胞舒張過程似較依賴醯解所釋出能量，故 Purkinje 纖維收縮舒張過程較快，收縮期間
  較短。
  n
• 英文摘要： Effects of tetrodotoxin (TTX), 2-deoxyglucose (2-DG) and pyruvate on the electrical and mechanicalactivity of isolated canine Purkinje fiber strands were studied to determine the role of Na influx and gly-colytic metabolism in the maintenance of the action potential plateau and the twitch duration of thisconducting tissue. At a concentration of 1 × 10 gm/ml, TTX slightly reduced the rate of upstroke butmarkedly shortened the duration of action potential and depressed the contractile force of Purkinje fibers.Reduction of (Na) also shortened the duration of action potential but greatly enhanced the contractileforce. Twitch duration was increased significantly under metabolic inhibition induced by 10 mM 2-DGbut not under the induced by anoxia. Twitch duration was also increased by 10 mM pyruate which elevat-ed and prolonged the plateau in the presence of TTX. Comparative study in ventricular muscles showedthat the muscle fibers were much more resistant to the effects of TTX. Electron microscopic examinationrevealed the smaller and more slender mitochondria and the lack of transverse tubules in Purkinje fibers.The results indicate that the disproportionally long action potential plateau and short twitch duration inPurkinje fibers are closely related to the dominant TTX-sensitive Na influx and the glycolytic metabolismin this conducting tissue.
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