Bailey J R, Sephton D H, Driedzic W R
Department of Biology, Mount Allison University, Sackville, New Brunswick, Canada.
J Mol Cell Cardiol. 1990 Oct;22(10):1125-34. doi: 10.1016/0022-2828(90)90076-e.
Hearts from three species of fish with varying myoglobin content were perfused with stepwise changes in input perfusate PO2 from approximately 160 to 10 mmHg. Flow through the heart, rate of contraction, and afterload were kept constant. This standardized stroke volume and bulk flow of perfusate to the myocytes since these hearts are nourished by the fluid in the ventricular lumen. In some cases NaNO2 was added to the perfusion medium to decrease existing levels of functional myoglobin. Myoglobin-rich hearts were able to extract a constant amount of oxygen until perfusate PO2 had fallen below 80 mmHg. At this point oxygen uptake began to decline. These hearts consumed oxygen until input PO2 was 10 mmHg or less. When normoxic conditions were restored the myoglobin-rich hearts showed complete recovery. Performance was maintained at a constant level over the entire range of input PO2. Myoglobin-poor hearts and nitrite-treated hearts were unable to sustain constant levels of oxygen consumption in the face of a declining perfusate PO2. These hearts were unable to extract oxygen from the medium and failed at perfusate PO2's of 40 mmHg for naturally myoglobin-poor hearts and 30 mmHg for nitrite-treated hearts. Half-maximal oxygen consumptions were attained by myoglobin-rich hearts at lower input PO2's than either myoglobin-poor or nitrite-treated hearts. The impact of myoglobin in intact heart is apparent at relatively high extracellular PO2's (40-80 mmHg) in this model system.
用逐步改变输入灌注液的氧分压（从约160mmHg降至10mmHg）的方法，对三种肌红蛋白含量不同的鱼类心脏进行灌注。心脏的血流量、收缩率和后负荷保持恒定。由于这些心脏由心室内腔中的液体滋养，这就使灌注液的每搏输出量和总体流量标准化。在某些情况下，向灌注培养基中添加亚硝酸钠以降低功能性肌红蛋白的现有水平。富含肌红蛋白的心脏能够提取恒定数量的氧气，直到灌注液的氧分压降至80mmHg以下。此时，氧气摄取开始下降。这些心脏会消耗氧气，直到输入氧分压为10mmHg或更低。当恢复常氧条件时，富含肌红蛋白的心脏显示出完全恢复。在整个输入氧分压范围内，心脏功能维持在恒定水平。面对灌注液氧分压下降，肌红蛋白含量低的心脏和经亚硝酸盐处理的心脏无法维持恒定的氧气消耗水平。对于天然肌红蛋白含量低的心脏，在灌注液氧分压为40mmHg时就无法从培养基中提取氧气并衰竭；对于经亚硝酸盐处理的心脏，在灌注液氧分压为30mmHg时就出现衰竭。富含肌红蛋白的心脏在比肌红蛋白含量低的心脏或经亚硝酸盐处理的心脏更低的输入氧分压下达到最大耗氧量的一半。在这个模型系统中，在相对较高的细胞外氧分压（40 - 80mmHg）下，肌红蛋白对完整心脏的影响是明显的。
