Dose--response curve for ethylnitrosourea-induced specific-locus mutations in mouse spermatogonia.

Abstract

The extreme mutagenic effectiveness of N-ethyl-N-nitrosourea in the mouse permitted the accumulation of the most extensive dose-response data yet obtained for chemical induction of specific-locus mutations in spermatogonia. In the lower portion of the curve, below a dose of 100 mg/kg, the data fall statistically significantly below a maximum likelihood fit to a straight line. Over this dose range, ethylnitrosourea reaches the testis in amounts directly proportional to the injection dose. Despite the mutagenic effectiveness of ethylnitrourea, the spermatogonia are apparently capable of repairing at least a major part of the mutational damage when the repair process is not swamped by a high dose. This finding is important both in basic studies on the mutagenic action of chemicals in mammals and in risk estimation.