DNA adducts detected in human gastric mucosa.

Human gastrointestinal neoplasms are mostly developed from the mucosa, not from the adjacent muscle layer. DNA adducts in the mucosa and adjacent muscle layer of the non-tumoral part of stomach from 19 patients with gastric neoplasms and from six newborns were analyzed by 32P-postlabeling, and then compared them with those of representative colon or small intestine sample. Five kinds of mucosa-specific DNA adducts (G1-5) were found in all of the adult stomach samples, but were entirely absent from the adjacent muscle layers and from the newborn stomachs. In addition, several common background adducts were also present in both the mucosa and muscle layer. G2 was the same DNA adduct as Si2 in the small intestine and C1 in the colon, and G3 was the same as Si1 in the small intestine. Thus, it was demonstrated that the mucosa of the stomach was exposed to DNA-reactive substances.