EFFECTS OF RADIATION ON ENDOTHELIAL FUNCTION

Purpose: The response of endothelium to ionizing radiation was studied . Methods and Materials: The abdominal aorta in different experimental groups of rats was irradiated, and the response of arterial rings fro m the irradiated segments to norepinephrine, acetylcholine (ACh), and nitroglycerin (NTG) was studied. Nonirradiated thoracic segments in th e same experimental animals were used as as a central for comparisons. Two age-matched nonirradiated control groups were also studied. Resul ts: A poor endothelium-dependent vasodilator response was obtained wit h ACh in the irradiated rings and also in those not directly irradiate d; the endothelium-independent vasodilator response to NTG was preserv ed during the first 3 days after irradiation. By 6 months, both the en dothelium-dependent response and endothelium-independent response were impaired. Conclusions: Alterations in nitric oxide synthesis and/or r elease by the endothelium were observed during the early phase of radi ation in irradiated and nonirradiated segments. In the delayed phase o f radiation, endothelium-independent muscular relaxation was also affe cted. (C) 1998 Elsevier Science Inc.