- 作者： 林正一; 陳福權; 余金妹
- 作者服務機構： 國防醫學院藥理學系; 陽明醫學院藥理學科
- 中文摘要：
本研究以離體狗心室肌及Purkinje纖維為實驗標本，觀察咖啡因（Caffeine）在不同鈣離子濃度（0.2～8.1mM〔Ca〕）
Tyrode氏液中，對結構不同之心臟組織的影響。咖啡因縮短Purkinje纖維動作電位，但延長心室肌動作電位期間。
1～3mM咖啡因先增強後抑制Purkinje纖維收縮力：最初的收縮力加強作用不受〔Ca〕。影響，其後的收縮力抑制作用
隨咖啡因劑量及〔Ca〕升高而加深，5mM丙酮酸鈉可對抗此抑制作用。咖啡因（1-l0mM）的加強收縮作用在心室肌較明
顯，同時延長心肌收縮時間。在propranolol（3.4×10-6 M）處理後，咖啡因加強心肌收縮作用仍然存在，故此作用與交感
神經傳遞物無關。Papaverine（10-6～3×10-5M）亦有加強心肌收縮的效果，但papaverine縮短心肌收縮時間，其作
用與cAMP相似而與咖啡因顯然不同，故咖啡因加強心肌收縮的效果似與其抑制磷酸雙脂?的作用無關。以上結果顯示咖
啡因主要作用在心肌Ca存儲部位（即肌漿網質）加強Ca之釋放，並抑制其重吸收，因而加強心肌收縮力；但如造成過量
Ca蓄積則可能抑制心肌收縮力。Purkinje纖維較易出現收縮力抑制現象，顯示其調節鈣離子功能不如心室肌。) - 英文摘要： The effects of caffeine on the electrical and mechanical activity of isolated canine ventricularmuscles and Purkinje fibers were studied in different [Ca] Tyrode solutions. Caffeine (1-3 mM) inducedratner small changes in the action potential configuration although the inotropic ettect of catteine waspronounced. In Purkinje fibers, caffeine induced a transient increase in contractile force followed by asubsequent decrease· The initial increase was about the same when exposed to different [Ca] (0.2, 2.7and 8.1 mM), but the higher the caffeine or Ca concentration, the greater the fall. Pyruvate (5 mM) reducedor even reversed the negative inotropic effect of caffeine in Purkinje fibers. Caffeine (1-10 mM) provokeda greater and longer-lasting positive inotropic effect in ventricular muscles than in Purkinje fibers and itincreased the duration of contraction. The positive inotropic effect of caffeine persisted after propranolol(3.4 x 10-6 M) treatment. Papaverine (10-6 ~3 x 10-5 M), a potent phosphodiesterase inhibitor, alsoinduced a positive inotropic effect in cardiac muscle but (in contrast to caffeine) reduced the time to peaktension and twitch duration. Thus the inotropic effect of caffeine is likely independent of its action onphosphodiesterase activity. The above findings are consistent with an action of caffeine on the sarcoplasmicreticulum (SR) which leads to an enhanced release of calcium and a block of calcium reuptake into the SR.The higher sensitivity of Purkinje fibers versus ventricular muscles to the negative inotropic effect ofcaffeine suggests that Purkinje fibers have a limited calcium buffering capacity.
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- 英文關鍵字： --
