Coefficient induction of pepsinogen 1-decreased pyloric glands and gastric cancers in five different strains of rats treated with N-methyl-N'-nitro-N-nitrosoguanidine

Sequential changes of numbers of pepsinogen 1 (Pg 1)-decreasedpyloric glands (PDPG) detected by immunohistochemistry and ofthe incidence of gastric carcinomas were examined in five differentstrains of rats treated with N methyl-N'-nitro-N-nitrosoguanidine(MNNG;CAS:70–25–7). Male SD (Crj:CD), WKY (WKY/NCrj),Lewis (LEW/Crj), Wistar (Crj:Wistar) and E344 (F344/DuCrj) rats(40 per strain), were given drinking water containing 100 µg/mlMNNG for 30 weeks and thennormal tap water, and were killedat week 10, 30 and 50 of the experiment. Adenocarcinomas ofthe glandular stomach were found in nine of 15 SD rats (60%),in eight of 12 WKY rats (67%), in eight of 15 Lewis rats (53%),in three of 13 Wistar rats (23%) andin one of 18 F344 rats (6%)at week 50. These incidences of carcinomas in SD, WKY and Lewiswere significantly higher (P < 0.01) than that in E344 rats.From week 10, the numbers of PDPG in SD, WKY and Lewis ratswere significantly greater (P < 0.01) than that in K344 rats.From week 30, the numbers of PDPG in Wistar rats were also significantlygreater (P < 0.05–0.01) than that of E344. The susceptibilityof rats to induction of gastric carcinoma by MNNG correlatedwith the susceptibility to induction of PDPG by MNNG in eachstrain, suggesting that induction of PDPG is a preneoplasticchange in chemical gastric carcinogenesis.