Hudlicka O, Wright A J, Hoppeler H, Uhlmann E
Department of Physiology, University of Birmingham Medical School, U.K.
Respir Physiol. 1988 Apr;72(1):1-12. doi: 10.1016/0034-5687(88)90074-6.
Blood flow and oxygen consumption were estimated in isolated hearts from control rabbits or animals with chronic bradycardia achieved by transvenous atrial pacing for 4 weeks; these parameters were related to ultrastructural changes. Chronic reduction of heart frequency to about 50% of control values resulted in an increased capillary/fibre ratio (1.43 +/- 0.07 in paced, 1.26 +/- 0.07 in control hearts), increased capillary density (2339 +/- 148 vs 1897 +/- 95) and increased volume density of mitochondria (36.36 +/- 1.28% vs 31.38 +/- 1.7%), in paced and control hearts, respectively, with no signs of heart hypertrophy (fibre diameters 28.5 micron in both groups). Maximal blood flow (3 ml.g-1.min-1) was similar in paced and control hearts. Maximal oxygen consumption (achieved by a gradual increase in preload and increase in force of contraction by noradrenalin infusion) in paced hearts was significantly higher than in control hearts and was achieved by a higher oxygen extraction. This could be due both to the increased volume density of mitochondria and to a more homogeneous distribution of flow through an enlarged capillary bed. The increased oxidative capacity induced by chronic bradycardial pacing can explain improved maximal cardiac work found under these conditions previously in vivo.
在对照兔或通过经静脉心房起搏4周实现慢性心动过缓的动物的离体心脏中估计血流量和氧耗量；这些参数与超微结构变化相关。将心率长期降低至对照值的约50%导致毛细血管/纤维比率增加（起搏心脏中为1.43±0.07，对照心脏中为1.26±0.07），毛细血管密度增加（分别为2339±148和1897±95），线粒体体积密度增加（分别为36.36±1.28%和31.38±1.7%），起搏心脏和对照心脏均无心脏肥大迹象（两组纤维直径均为28.5微米）。起搏心脏和对照心脏的最大血流量（3毫升·克⁻¹·分钟⁻¹）相似。起搏心脏的最大氧耗量（通过逐渐增加前负荷和输注去甲肾上腺素增加收缩力实现）显著高于对照心脏，且通过更高的氧摄取实现。这可能是由于线粒体体积密度增加以及通过扩大的毛细血管床的血流分布更均匀。慢性心动过缓起搏诱导的氧化能力增加可以解释先前在体内这些条件下发现的最大心脏功改善的原因。
