Radiation Hypertension and Nephrosclerosis

Rats given single x-ray doses to the whole body or whole-body with temporarily exteriorized kidneys shielded (300 R or 500 R) or to the temporarily exteriorized kidneys only (300 R, 500 R or 1000 R), together with their surgical and nonsurgical sham-irradiated control rats, were studied periodically for 17 months or longer postexposure for systolic blood pressure and renal histopathology. Increased systolic blood pressure, above the time-dependent increases in nonirradiated animals, was induced by all doses and modes of irradiation; the increases were dose-dependent and time-dependent, but independent of the mode of irradiation at given dose levels. Progressive arteriolonephrosclerosis, greater in degree at given times than that in nonirradiated animals, was induced by all doses and modes of irradiation in dose-dependent fashion. Nephrosclerosis progressed more rapidly in animals whose kidneys were irradiated, less rapidly in those whose kidneys were shielded during irradiation, and least rapidly in nonirradiated animals. The initiation of blood pressure increase by renal irradiation required little renal damage, and this was apparently limited to subtle degenerative and occlusive changes in fine vasculature, especially cortical arterioles. Much of the progressive nephrosclerotic process developed after the rise of blood pressure, apparently partly as a result of the hypertension.