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Response of swine skin microvasculature to acute single exposures of X rays: quantification of endothelial changes.

An acute single X-ray exposure of 2300 R produces in swine skin a moist reaction (ulceration) that appears at 17 days, heals by 32 days, and may break down again between 42 and 70 days. Initial studies quantified the epidermal population density changes during this 70-day period. This study was designed to quantify the density changes occurring in the endothelial cell population of the dermal microvasculature. While the basal population decreases to a nadir of 10% control by 24 days, the endothelial population remains at control levels. Beyond 24 days, the endothelial cell density decreases abruptly to 50% as the epidermal cell density returns to control levels and overshoots by 20% at 32 days. Subsequently, both populations decrease to zero by 57 days. Endothelial cell loss parallels a similar decrease in vascular lumen density. These findings indicate that the initial moist reaction results from a radiation-induced loss of epidermal cells, while the second reaction results from the loss of dermal microvasculature.