Late effects of ionizing radiation on the microvascular networks in normaltissue

Damage to the microvascular networks constitutes one of the most important components of ionizing radiation damage to normal tissue, Previously, we ha ve reported the early (3, 7 and 30 days postirradiation) effects of ionizin g radiation on the structure and function of normal tissue microvascular ne tworks, Here we report on the late effects of ionizing radiation on the str uctural and functional changes in microvascular networks in locally irradia ted (single 10-Gy dose) hamster cremaster muscles observed 60, 120 and 180 days postirradiation; age-matched animals were used as controls. As in the previous study, intravital microscopy was used to measure structural and fu nctional parameters in complete microvascular networks in vivo. A factorial design was used to examine the effects of radiation status, time postirrad iation, and network vessel type on the structure and function of microvascu lar networks. Our results indicate that the progression of radiation-induce d microvascular damage continues during the late times but that there is pa rtial recovery from radiation damage within 6 months postirradiation, Red b lood cell flux, red blood cell velocity, and capillary blood flow in irradi ated networks at 180 days postirradiation were significantly greater than c ontrol levels. As at the early times, all vessel types were not damaged equ ally by radiation at every time. (C) 2000 by Radiation Research Society.