In vivo binding of N-nitrosopyrrolidine and N-nitrosohexamethyleneimine to non-purine sites on rat liver DNA

Liver DNA and RNA were isolated from rats treated with the liver carcinogens N-nitrosopyrrolidine (NPYR) and N-nitrosohexamethyleneimine (NHX). After hydrolysis in 70% perchloric acid (100°C, 1.0 h), 70% of the radioactivity in both the DNA and RNA hydrolysates chromatographed as a single peak. The material from both hydrolysates had comparable R_f values on cation exchange and Sephadex G-10 chromatography. Subsequent experiments indicated this material was volatile. After depurination (0.1 M HCl) of the DNA from NPYR- and NHX-treated rats, Sephadex G-10 chromatography separated only a single radio-active peak which co-eluted with the apurinic acid at the void volume. The material which comprised this peak was not volatile. After dialysis of the same 0.1 M HCl hydrolysate from NHX-treated rats, 98% of the radio-activity remained attached to the apurinic acid. These 2 cyclic nitrosamines appear to produce alkylating species that: (10 are capable of extensive, if not exclusive, phosphotriester formation; or (2) have 2 active sites that cross-link to keep purines attached to apurinic acid after 0.1 M HCl hydrolysis.