頁籤選單縮合
題名 | Low Oxygen Tension Induces Positive Inotropy and Decreases a [fed7] in Isolated Guinea-Pig Cardiac Ventricular Papillary Muscles |
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作者 | Yang,Jung-mou; Jao,Ming-jy; | 書刊名 | 中國生理學雜誌 |
卷期 | 41:2 1998.06[民87.06] |
頁次 | 頁101-106 |
分類號 | 437.657 |
關鍵詞 | Intracellular Na狇activity; Na狇K狇pump; Guinea-pig cardiac ventricular papillary muscle; Hypoxia; Reserpine; |
語文 | 英文(English) |
英文摘要 | Effects of low oxygen on contractile force, intracellular Na�吧ctivity (a�[���f), and action potential were simultaneously measured in isolated guinea-pig ventricular papillary muscles. Reduction of oxygen from control 448 to 150 mmHg biphasically increased and decreased and decreased the twitch tension, and decreased a�[���f in muscles driven at 60 beats/min. The action potential duration (ADP) was decreased but the maximun rate of upstroke (V��) was increased. In control, 1μM epinephrine significantly increased the the action potential amplitude and twitch tension with decreases in the time to twitch peak (TTP), time for 50% relaxation (RT�t), and a�[���f. After exposure to low oxygen for 10 min, with twitch tension elevated and TTP and RT increased, 1μM epinephrine significantly increased the twitch tension and V�� , and decreased the ADP and a�[���f. Pretreatment with reserpine inhibited the twitch tension, both at control and in the presence of epinephrine. But changes of action potential and a�[���f in response to low oxygen and epinephrine were similar to thoes in control. Our results indicate that the isolated guinea-pig ventricular muscle needs a high oxygen tension to maintain a normal contractile function. Reduction of oxygen deteriorates the electrical and mechanical activities, most likely, by a coaxial graded hypoxia. The decreased a�[���f, not associated with endogenous catecholamines, suggests that the activity of the Na��- K�� pump can be maintained in the superficial muscle cells despite of corecentral hypoxia. |
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