Microvascular development during normal growth and reduced blood flow: introduction of a new model.
The purpose of this study was to evaluate microvascular development during normal skeletal muscle maturation and to determine the alterations associated with decreased blood flow caused by a decrease in demand. Unilateral orchidectomy was performed on 4-wk-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 when compared with 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.
Wang
D H
DH
Department of Physiology, Eastern Virginia Medical School, Norfolk 23501.
Prewitt
R L
RL
D000818:Animals; D001160:Arterioles / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology; D001783:Blood Flow Velocity; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008954:Models, Biological; D024510:Muscle Development; D009132:Muscles / Q000098:blood supply* / Q000502:physiology; D009919:Orchiectomy; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow