Ritter L S, Wilson D S, Williams S K, Copeland J G, McDonagh P F
Department of Surgery, University of Arizona, Tucson, USA.
Microcirculation. 1995 Dec;2(4):315-27. doi: 10.3109/10739689509148276.
The pathobiology of leukocyte sequestration in the coronary microcirculation following ischemia is unclear. We examined the location(s) and persistence of leukocyte sequestration of unactivated and preactivated blood in the coronary microcirculation early during reperfusion following ischemia.
Isolated rat hearts were subjected to 30 min of 37 degrees C, no-flow ischemia. Hearts were initially reperfused with diluted whole blood containing fluorescent leukocytes (DWB*). At 5, 20, and 35 min of reperfusion (R), the deposition of leukocytes in the coronary capillaries and venules was observed directly using intravital fluorescence microscopy. Four groups were studied: a nonischemic control group (Gr I), and postischemic groups reperfused with DWB* treated with vehicle (Gr II) or preactivated with 10(-8) M N-formylmethionyl-leucyl-phenylalanine (fMLP) (Gr III) or 10(-6) M fMLP (Gr IV).
At R5, postischemic reperfusion with unactivated blood caused a significant trapping of leukocytes in coronary capillaries (Gr I = 2.2 +/- 0.4 versus Gr II = 5.6 +/- 0.6 leukocytes per capillary field, P < 0.05). Hearts in Gr IV exhibited significantly greater leukocyte retention in capillaries compared to all other groups at R5 (R5, Gr IV = 8.8 leukocytes per capillary field, P < 0.05) and at R35. At R5, although more leukocytes were observed adhered to the venules in Gr II compared to Gr I, the difference was not statistically significant (Gr I = 1.7 +/- 0.7 versus Gr II = 3.4 +/- 0.5 leukocytes per 100 microns venule, P = 0.23). DWB* preactivated with the lower concentration of fMLP (10(-8) M) resulted in a significant increase in venular leukocyte adhesion at R5 compared to Gr I and Gr II (Gr III 6.1 +/- 0.5, P < 0.05). After 35 min of reperfusion, a greater percentage of leukocytes remained in the capillaries than in the venules.
These direct observations suggest that early in reperfusion after ischemia, both leukocyte and endothelial activation are necessary for venular adhesion, but that ischemia-induced coronary microvascular alterations are sufficient to promote leukocyte retention in coronary capillaries. These results also indicate that during 35 min of reperfusion, the degree of leukocyte washout is greater in the venules than in the capillaries. These results suggest that the mechanisms contributing to leukocyte retention early in reperfusion following myocardial ischemia are, indeed, different in the capillaries and venules and that the mechanisms affecting retention in capillaries are more persistent than those in the venules.
缺血后冠状动脉微循环中白细胞滞留的病理生物学机制尚不清楚。我们研究了缺血后再灌注早期未激活和预激活血液中白细胞在冠状动脉微循环中的滞留位置及持续时间。
将离体大鼠心脏置于37℃无血流状态下缺血30分钟。心脏最初用含有荧光白细胞的稀释全血（DWB*）进行再灌注。在再灌注（R）5分钟、20分钟和35分钟时，使用活体荧光显微镜直接观察冠状动脉毛细血管和小静脉中白细胞的沉积情况。研究了四组：非缺血对照组（I组），以及缺血后用载体处理的DWB再灌注组（II组）或用10⁻⁸M N-甲酰甲硫氨酰-亮氨酰-苯丙氨酸（fMLP）预激活的DWB再灌注组（III组）或10⁻⁶M fMLP预激活的DWB*再灌注组（IV组）。
在R5时，用未激活血液进行缺血后再灌注导致冠状动脉毛细血管中白细胞明显滞留（I组=每毛细血管视野2.2±0.4个白细胞，II组=每毛细血管视野5.6±0.6个白细胞，P<0.05）。IV组心脏在R5时（R5，IV组=每毛细血管视野8.8个白细胞，P<0.05）和R35时，毛细血管中的白细胞滞留明显多于所有其他组。在R5时，尽管与I组相比，II组中观察到更多白细胞粘附于小静脉，但差异无统计学意义（I组=每100微米小静脉1.7±0.7个白细胞，II组=每100微米小静脉3.4±0.5个白细胞，P=0.23）。用较低浓度fMLP（10⁻⁸M）预激活的DWB*导致R5时小静脉白细胞粘附较I组和II组显著增加（III组6.1±0.5，P<0.05）。再灌注35分钟后，留在毛细血管中的白细胞百分比高于小静脉。
这些直接观察结果表明，在缺血后再灌注早期，白细胞和内皮细胞激活对于小静脉粘附都是必要的，但缺血诱导的冠状动脉微血管改变足以促进白细胞在冠状动脉毛细血管中的滞留。这些结果还表明，在35分钟的再灌注期间，小静脉中白细胞的清除程度大于毛细血管。这些结果表明，心肌缺血后再灌注早期导致白细胞滞留的机制在毛细血管和小静脉中确实不同，且影响毛细血管中滞留的机制比小静脉中的更持久。
