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Influence of Altitude on Late Effects of Radiation in RF/Un Mice: Observations on Survival Time, Blood Changes, Body Weight, and Incidence of Neoplasms¹

Laboratorio de Investigacion de Cancer, Instituto de Investigaciones de la Altura, Universidad Peruana "Cayetano Heredia," Lima, Peru [P. M. C., M. S. J.], and Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 [A. C. U. and J. W. C.]

RF female mice were sham-irradiated (as controls) or given 150 or 300 R X-rays to the whole body at 10 weeks of age and kept for the duration of their lives either at sea level or high altitude (14,900 feet).

On ascent to high altitude, the mice showed a rapid, marked erythropoietic response, which was not detectably impaired by earlier irradiation. With advancing age, the erythrocyte count and hemoglobin level gradually increased in the mice at high altitude, whereas the reverse occurred in the mice kept at sea level. As the mice aged the granulocyte count also increased, but the mononuclear cell count decreased; neither change was detectably affected by irradiation or altitude.

The life-span of the mice decreased with increasing radiation dose and was shorter in all groups (including controls) at high altitude than at sea level. Body weight gain was impaired in mice at high altitude, and the overall incidence of neoplasms was lower than in the mice at sea level.

Incidence of thymic lymphomas and granulocytic leukemias increased with irradiation, whereas the reverse was true with other lymphomas and leukemias. In general, at any given dose level all such growths were less common at high altitude than at sea level.

Incidence of lung tumors decreased with irradiation in mice maintained at sea level but increased in mice maintained at high altitude, especially when the incidence was adjusted to correct for differences in survival time. Pulmonary carcinomas were more common at high altitude than at sea level.

Incidence of ovarian tumors was increased by radiation but was unaffected by altitude. Ovarian telangiectatic and angiomatoid lesions, on the other hand, were more prevalant at high altitude than at sea level.

Miscellaneous neoplasms of other types and at other sites were observed sporadically in all experimental groups, but at a frequency too low to disclose any definite effects of radiation and altitude.

Telangiectasias in various organs and mural thrombosis of the endocardium were prevalent at high altitude, although rare at sea level. Similarly, interstitial myocarditis, rare at sea level, was more common at high altitude and was occasionally associated with thrombosis of the endocardium. Occurrence of these lesions was not significantly affected by radiation. Nephrosclerosis occurred in nearly all aging mice at sea level, with or without irradiation; it occurred less commonly in mice at high altitude, in which its incidence was increased by irradiation.

¹ This research was sponsored by the Biology Division, National Cancer Institute-Atomic Energy Commission Carcinogenesis Program, Oak Ridge National Laboratory, Oak Ridge, Tenn., and supported in part by Research Grant CA-06597 from the National Cancer Institute, NIH, USPHS, and by Research Grant DRG-726 from the Damon Runyon Memorial Fund for Cancer Research, Inc.

² Present address: Health Sciences Center, State University of New York at Stony Brook, Stony Brook, N. Y. 11790.

Received 6/30/69. Accepted 9/17/69.