Tschubar F, Rose H, Kammermeier H
Department Physiologie, Medical Faculty RWTH Aachen, Klinikum, FRG.
J Mol Cell Cardiol. 1993 Apr;25(4):355-66. doi: 10.1006/jmcc.1993.1042.
Interstitial transudate of isolated isometrically working perfused rat hearts was analyzed to investigate fatty acid (FA) release and transfer across the capillary wall. Unsaturated FA were released under certain conditions. Lowering medium FA (16:0) with constant or varying FA/A-ratio (A: albumin) decreased interstitial FA-concentration down to 17% of arterial FA-concentration. This was accompanied by reduced uptake-rate. Transcapillary diffusion-resistance, unless markedly altering, cannot be responsible for this observation. Calculated diffusion-rates of FA and FA* protein-complexes in the endothelial cytoplasm and interstitium indicate that FA-transfer takes place almost exclusively bound to carrier-proteins. The apparent permeability surface-area-values of FA for transendothelial FA-transfer are three orders of magnitude higher than those for sucrose; diffusion-coefficients for FA across the endothelium are close to those in water, excluding substantial diffusion-barrier of the capillary wall. Dissociation-rate-constants calculated from experimental data are in the range of those reported for FA* albumin-complexes in vitro. Thus the observed transcapillary FA-gradients are apparently due to the limited dissociation-rate of the FA*albumin-complex in the intravascular space.
分析离体等长收缩灌注大鼠心脏的间质渗出液，以研究脂肪酸（FA）穿过毛细血管壁的释放和转运。在某些条件下不饱和脂肪酸会释放出来。在脂肪酸/白蛋白（A：白蛋白）比值恒定或变化的情况下降低培养基中的脂肪酸（16:0），可使间质脂肪酸浓度降至动脉脂肪酸浓度的17%。这伴随着摄取率的降低。除非有明显改变，跨毛细血管扩散阻力不能解释这一现象。计算得出的脂肪酸和脂肪酸蛋白质复合物在内皮细胞质和间质中的扩散速率表明，脂肪酸转运几乎完全是与载体蛋白结合进行的。脂肪酸跨内皮转运的表观通透表面积值比蔗糖的高三个数量级；脂肪酸穿过内皮的扩散系数接近其在水中的扩散系数，排除了毛细血管壁存在实质性扩散屏障的可能性。根据实验数据计算出的解离速率常数与体外报道的脂肪酸白蛋白复合物的解离速率常数范围相同。因此，观察到的跨毛细血管脂肪酸梯度显然是由于脂肪酸*白蛋白复合物在血管内空间的解离速率有限所致。
