Carvalho Helena, Pittman Roland N
Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, Brazil.
Microcirculation. 2008 Apr;15(3):215-24. doi: 10.1080/10739680701616175.
The aim of this study was to determine longitudinal and radial gradients in oxygen tension (PO(2)) in microvessels of the hamster cheek pouch.
We measured PO(2) using the phosphorescence-quenching method in two orders of arterioles (45.8 +/- 5.5 and 19.9 +/- 1.8 micro m diameter), capillaries, and two orders of venules (50.5 +/- 3.4 and 21.4 +/- 2.0 micro m diameter) in order to determine the longitudinal PO(2) gradient. At the arteriolar and venular sites, we also measured PO(2) at four different sites for an analysis of radial PO(2) gradients: centerline, inside wall (larger arteriole and venule only), outside wall, and interstitium. We used 10 hamsters weighing 115 +/- 27 g anesthetized with pentobarbital intraperitoneally and maintained with alpha-chloralose intravenously. The cheek pouch was everted and a single-layered preparation was studied by intravital microscopy. Albumin-bound Pd-porphyrin was infused into the circulation and excited by flash illumination at 10 Hz, with a rectangular diaphragm limiting the excitation field to 5 x 25 micro m.
In the longitudinal direction, intravascular PO(2) decreased significantly (P < 0.01) from large arterioles (39.5 +/- 2.3 mmHg) to small arterioles (32.2 +/- 0.3 mmHg), then to capillaries (30.2 +/- 1.8 mmHg), and on to small venules (27.3 +/- 2.1 mmHg) and large venules (25.5 +/- 2.2 mmHg). In the radial direction, PO(2) decreased significantly (P < 0.01) in and around larger arterioles, and to a lesser extent, around the smaller ones (P < 0.05). There was no significant PO(2) gradient, longitudinal or radial, associated with venules. The PO(2) difference from the centerline to the outside wall in large arterioles was 8.3 +/- 1.4 mmHg, and most of the decline in PO(2) in the radial direction was contributed by the intravascular difference (4.7 +/- 2.1 mmHg) and only about 1.0 +/- 2.7 mmHg by the transmural difference.
Our data show that there are large intra-arteriolar radial PO(2) gradients, but no large transmural PO(2) differences, suggesting that the oxygen consumption of the microvessel wall is not exceptionally high.
本研究旨在测定仓鼠颊囊微血管中氧分压（PO₂）的纵向和径向梯度。
我们采用磷光猝灭法测量了两级小动脉（直径分别为45.8±5.5和19.9±1.8μm）、毛细血管以及两级小静脉（直径分别为50.5±3.4和21.4±2.0μm）中的PO₂，以确定纵向PO₂梯度。在小动脉和小静脉部位，我们还在四个不同位点测量了PO₂，用于分析径向PO₂梯度：中心线、内壁（仅较大的小动脉和小静脉）、外壁以及间质。我们使用了10只体重为115±27g的仓鼠，通过腹腔注射戊巴比妥麻醉，静脉注射α-氯醛糖维持麻醉状态。将颊囊外翻，通过活体显微镜研究单层制剂。将白蛋白结合的钯卟啉注入循环系统，并以10Hz的闪光照明激发，用矩形光阑将激发场限制在5×25μm。
在纵向，血管内PO₂从大动脉（39.5±2.3mmHg）到小动脉（32.2±0.3mmHg），再到毛细血管（30.2±1.8mmHg），然后到小静脉（27.3±2.1mmHg）和大静脉（25.5±2.2mmHg）显著下降（P<0.01）。在径向，较大小动脉及其周围的PO₂显著下降（P<0.01），较小小动脉周围的PO₂下降程度较小（P<0.05）。小静脉不存在显著纵向或径向PO₂梯度。大动脉中心线到外壁的PO₂差值为8.3±1.4mmHg，径向PO₂的下降主要由血管内差异（4.7±2.1mmHg）导致，跨壁差异仅约为1.0±2.7mmHg。
我们的数据表明，小动脉内存在较大的径向PO₂梯度，但跨壁PO₂差异不大，这表明微血管壁的氧消耗并非异常高。
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