Invited Symposium: Hypertension III: Flow-Induced Vascular Remodeling
Prewitt, RL. (Department of Physiology, Eastern Virginia Medical School, VA, USA)
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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|Wang, DH.; Prewitt, RL.; (1998). Microvascular Adaptations to Reduced Blood Flow: Introduction of a New Model. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/prewitt/wang0894/index.html|
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