Mathieu-Costello O
Department of Medicine, University of California, San Diego, La Jolla 92093.
Respir Physiol. 1989 Jun;76(3):289-302. doi: 10.1016/0034-5687(89)90070-4.
At given capillary-to-fiber ratio and sarcomere length, capillary tortuosity determines capillary length and the geometry of blood-tissue exchange in muscles. It is therefore an important determinant of the potential efficiency of O2 supply to the muscle fibers. Reports have indicated that capillary tortuosity increases with adaptation to hypoxia. Unfortunately, sarcomere length was not taken into account. Because capillary tortuosity increases substantially as the muscle shortens, it is important to measure sarcomere length when comparing capillary configuration among muscles. We addressed the question of whether or not capillary tortuosity is greater in skeletal muscles of high altitude mice compared to sea-level, when account is taken of sarcomere length. Calf and thigh muscles of high altitude (3800 m; inspired PO2, 91 mm Hg) and sea-level deer mice, Peromyscus maniculatus, were perfusion-fixed in situ at sarcomere lengths ranging from 1.9 to 2.4 microns. Capillary-to-fiber ratio, capillary length per volume of fiber, and the degree of orientation (anisotropy) of capillaries were estimated by morphometry. In both sea-level and high altitude mice, capillaries were relatively straight in extended muscles, and substantially more tortuous in muscles fixed at shorter sarcomere length. There was no systematic difference in the degree of tortuosity of capillaries in the high altitude compared to sea-level mice, when account was taken of sarcomere length. Capillary length per volume of muscle fiber and capillary-to-fiber ratio were not significantly different between the two groups.
在给定的毛细血管与肌纤维比例及肌节长度条件下，毛细血管迂曲度决定了毛细血管长度以及肌肉中血液与组织间交换的几何形态。因此，它是肌肉纤维氧气供应潜在效率的一个重要决定因素。有报告指出，毛细血管迂曲度会随着对低氧的适应而增加。遗憾的是，当时未考虑肌节长度。由于随着肌肉缩短，毛细血管迂曲度会大幅增加，所以在比较不同肌肉的毛细血管形态时，测量肌节长度很重要。我们探讨了一个问题：在考虑肌节长度的情况下，与海平面小鼠相比，高海拔小鼠骨骼肌中的毛细血管迂曲度是否更大。将高海拔（3800米；吸入氧分压为91毫米汞柱）和海平面的鹿鼠（白足鼠）的小腿和大腿肌肉在肌节长度为1.9至2.4微米的范围内进行原位灌注固定。通过形态测量法估算毛细血管与肌纤维比例、每单位肌纤维体积的毛细血管长度以及毛细血管的定向程度（各向异性）。在海平面和高海拔小鼠中，毛细血管在伸展的肌肉中相对较直，而在肌节长度较短时固定的肌肉中则明显更迂曲。在考虑肌节长度的情况下，与海平面小鼠相比，高海拔小鼠毛细血管的迂曲程度没有系统性差异。两组之间每单位肌纤维体积的毛细血管长度和毛细血管与肌纤维比例没有显著差异。
