<原著>覚醒犬を用いた心筋反応性充血の機序に関する研究

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To study the contribution of myogenic factor to myocardial reactive hyperemia, we measured the reactive hyperemic flow produced by a brief left circumflex coronary artery occlusion in 7 chronically instrumented conscious dogs. The experiment consisted of a single occlusion (experiment A) and repeated occlusion (experiment B). The occlusion time of experiment A was 1 second, or 3,5,7,10 or 20 seconds. In experiment B, the first occlusion time was 3,5 or 10 seconds and the second one was 3 seconds only. The release time between the first and the second occlusion was 3,5 or 10 seconds, respectively. Both experiments were performed before and after administration of phentolamine, propranolol, diltiazem, ergonovine and dipyridamole in each separate day. In experiment A, 1 second occlusion induced a significant reactive hyperemia and the repayment of flow debt was 276±25%. Reactive hyperemic flow increased as occlusion time was increased. The increment of excess flow between the 3 to the 5 second occlusion was greater than those between the other occlusion times. All the drugs used except ergonovine tended to decrease reactive hyperemia as compared to the control experiment, especially dipyridamole administration induced significantly smaller repayment of flow debt compared with the control. When preocclusion coronary artery blood flow was increased irrespective of the causes of the increased flow, reactive hyperemic flow was decreased. In experiment B, repeated occlusion after the first occlusion of 10 seconds produced a small total excess flow as compared with that of single 10 second occlusion. On the contrary, repeated occlusion after the first occlusion of 3 seconds showed a reverse result. When the first occlusion time was 3 or 5 seconds, the second occlusion produced smaller reactive hyperemia than that produced by the single 3 second occlusion. Repeated occlusions after intervention of the drugs showed almost the same results except for dipyridamole. Excess flow II after phentolamine administration was greater than that after propranolol administration. These findings suggest that there are many factors contributing to myocardial reactive hyperemia. Coronary occlusion time more than 3 seconds may cause a powerful vasodilator reaction due to myocardial ischemia. In the coronary occlusion time of 3 seconds or shorter, however, other factors may contribute to the reactive hyperemia instead of the metabolites.
1987-09-25

<原著>覚醒犬を用いた心筋反応性充血の機序に関する研究

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