The dose-response relationship for ultraviolet-light-induced mutations at the hypoxanthine-guanine phosphoribosyltransferase locus in Chinese hamster ovary cells

Abstract

Exposure of Chinese hamster ovary (CHO) cells clone K ₁BE₄ to ultraviolet (UV) light at doses up to 86 ergs/mm² did not significantly reduce cell survival, but UV doses of 86–648 ergs/mm² produced an exponential cell killing. Observed mutation frequency to 6-thioguannine resistance induced by UV increases approximately in proportion to increasing doses up to 260 ergs/mm² in a range of 5–648 ergs/mm² examined. The pooled data of mutation frequency f(X) as a function of dose X from 0–260 ergs/mm² is adequately described by f(X)=10⁻⁶ (13.6+2.04 X). That the UVinduced mutations to 6-thioguanine resistance affects the hypoxanthineguanine phosphoribosyltransferase (HGPRT) locus is supported by the observation that all randomly isolated drugresistant colonies contained highly reduced or undetectable HGPRT activity.