Carcinogenic Properties of Increased Oxygen Tensions. I. Effects on Radiation-Induced Mammary Tumors<xref ref-type="fn" rid="FN2">2</xref>

Abstract

It has been reported that exposure to increased oxygen concentrations will enhance the incidence of chemically induced tumors in the lungs of mice. Such effects of oxygen on neoplastic transformation are important in hyperbaric medicine and space programs. To investigate more fully the carcinogenic-enhancing properties of oxygen, we studied the relationship of increased oxygen tensions on radiation-induced mammary tumors in the female Sprague-Dawley rat. The animals were exposed to the following regimen 1 week after 400 rads whole-body irradiation: 1 hour daily, 5 consecutive days a week for 6 weeks to either 1 atmospheres absolute (ATA) air (Po2 152 mm Hg), 3 ATA air (Po2 456 mm Hg), 1 ATA oxygen (Po2 760 mm Hg), or 3 ATA oxygen (Po2 2280 mm Hg). The data indicate that increased oxygen tensions speed up the time of emergence of the primary tumors and enhance the incidence of tumors. Increases in the total number of tumors as well as the number of second tumors per animal were noted. The higher oxygen tensions produced no changes in location or histologic type of tumor.