Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

The purpose of this study was to evaluate microvascular development during normal skeletal muscle maturation, and determine the alterations associated with decreased blood flow caused by a decrease in demand. Unilateral orchidectomy was performed on 4-week-old rats to reduce muscle tension and growth of one cremaster muscle. Three weeks later, total blood flow was reduced to 58+9% measured by the dual-slit velocity technique and 55+9% by radioactive microspheres and the muscle was smaller compared to the intact contralateral muscle. Blood flow per gram of tissue was not significantly different. Measured by closed-circuit television microscopy, the internal diameters and wall cross-sectional areas of all orders of arterioles (1A - 4A), and the number of 4As per 3A had increased with age in the control muscle. The arcading arterioles increased in length by 35% as the intact muscle grew, but the number of 3As remained unchanged. Arteriolar length increased but not in proportion to muscle mass. As a result, large and small arteriolar density decreased with age. Thus, during normal skeletal muscle maturation, preexisting arterioles became elongated and only precapillary arterioles increased in number, resulting in a decreased ratio of arteriolar number to tissue mass. Unilateral orchidectomy inhibited the growth of arterioles in both size and number. A reduced diameter of the 1A in the orchidectomy muscle resulted in unchanged wall shear rate. Flow-induced shear stress and/or local changes in growth factors are suggested as possible mechanisms mediating the alterations.

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Presentation Number SAwang, 0894
Keywords: microcirculation, vascular growth, autoregulation, shear rate