Reaction of N-n-butyl-N-nitrosourea with DNA in vitro.

N-n-[1-14C]Butyl-N-nitrosourea was synthesized from n-[1-14C]butanol and incubated at physiological conditions (pH 7.2; 37 degrees C) with calf thymus DNA in vitro. Following mild acid hydrolysis, purine bases were separated by Sephadex G-10 and cation exchange chromatography. 3-n-Butyladenine, 7-n-butylguanine and O6-n-butylguanine were identified as major reaction products. The O6-/7-butylguanine ratio was 0.69, indicating that the relative extent of oxygen alkylation by n-butylnitrosourea is similar to that produced by ethylnitrosourea.