- 作者: 楊忠謀; 楊生湳; 林正一
- 作者服務機構: 國防醫學院生理學科; 國防醫學院藥理學科
- 中文摘要:
心房利鈉因子(ANF)和乙醯膽胺(ACh)分別是心臟組織產生的一種胜?激素與膽胺性的神經傳遞物質;兩者對心室
肌在電氣生理與收縮的直接作用尚無定論。本研究利用離體的天竺鼠右心室乳頭肌,以傳統玻璃微電極和張力轉能器同
時測量動作電位和收縮力的變化。心房利鈉因子(3,30,300 nM)在正常鉀離子濃度(4 mM)之Tyrode溶液和高鉀溶液
(鉀為27 mM)中對心室肌收縮力和動作電位快速反應與慢速反應均無顯著的作用。然而,乙醯膽胺(0.01 μM)在正常
的Tyrode溶液中即使動作電位期間縮短;於5 μM的濃度下,再極化50%和90%的期間分別減少了10.5±2.1%與
12.4±1.8%,收縮力卻增加了9.8±1.2%(n=6, p<0.05)。在26個標本中,有11個標本於實驗過程中產生自發性動
作電位,並與電刺激引發的動作電位混合出現。乙醯膽胺在1-5 μM濃度能?抑制心室肌自發性異位節律,這些抑制作
用可以被Atropine所阻斷;但是Atropine對乙醯膽胺增強心室肌收縮力卻無抑制的作用。實驗結果顯示心房利鈉因子在
生理濃度下對天竺鼠心室乳頭肌的收縮力與動作電位的發生無任何顯著影響;乙醯膽胺對心室肌動作電位的抑制作用是
經由胞膜上毒蕈素接受器的活化,但是收縮力的增加則經由其它的機轉。: - 英文摘要: The direct effects of atrial natriuretic factor (ANF) and acetylcholine (ACh) on isolated guinea-pigventricular papillary muscle were studied. ANF (3x10-9 - 3x10-7M), a cardiogenic hormone, had nosignificant electrical or mechanical effcets on guinea pig papillary muscle driven at a frequency of 60beats/min in normal (4 mM) and hlgh [K]0 (27 mM) Tyrode solutions. On the other hand, ACh (3x10-8-3x10-7M) caused a significant shortening of action potential duration and the contractile force showed nochange or a slight decrease. At high concentration (5 μM), ACh reduced action potential durations at 50%and 90% repolarization (APD50 and APD90) by 10.5 ± 2.1% and 12.4 ± 1.8%, respectively, but the con-tractile force was slightly increased by 9.8 ± 1.2%. In eleven of twenty-six preparations, spontaneousactivity occurred and intermlngled with driven activity. The ectopic rhythms were suppressed by ACh(l-5 μM). The changes in electrical but not mechanic activity induced by ACh were suppressed in thepresence of five micromolar atropine. These results reveal that, in guinea pig papillary muscle, ANF hadno direct chronotropic or inotropic effect. ACh may reduce APD and spontaneous discharges through anactivation of muscarinic receptors but enhance twitch tension through other mechanisms.
- 中文關鍵字: ANF; ACh; ventricular papillary muscle
- 英文關鍵字: --