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The present report is a study of the effect of the carcinogen nitrosomethylurea (NMU) on pancreas of rats receiving during lifetime a lipid-poor diet, that is essential fatty acid deficient or control diets. Rats fed a commercial stock chow were mated. At day 10 of pregnancy, dams were divided into three groups, that were respectively supplied with the commercial chow, the essential fatty acid deficient or the sufficient diet. Each litter was separated at random in two groups that received at day one of life one intraperitoneal injection of NMU (50 mg/kg b.w.) or saline. After weaning, they were maintained for life with the diet that was supplied to their mothers. The pancreas of NMU-treated rats presented diffuse proliferative changes, focal acinar cell hyperplasias (FACH), and focal hepatocyte-like metaplasia (FHLCM). FACH were expansive presumably preneoplastic growths, showing abnormal differentiation. The number of NMU-treated rats bearing FACH and FHLCM did not significantly differ in the three nutritional conditions.

Microspectrophotometric DNA measurements in exocrine pancreas of essential fatty acid-deficient (EFAD) and EFA-sufficient (EFAS) rats which received a single intraperitoneal injection of the carcinogen nitrosomethylurea (NMU) or saline (SAL) was the subject of the present report. The DNA content of acinar pancreatic cells of SAL-injected EFAD and EFAS rats was diploid. NMU-induced pancreatic focal acinar cell hyperplasia (FACH) had one main cell population with a diploid content, whereas in the intervening parenchyma there were diploid and tetraploid cells. The number of tetraploid cells was smaller in EFAD rat pancreas than in EFAS indicating a diet dependent effect. NMU-induced FACH had a diploid distribution pattern indicating that cells are in a G1, quiescent phase, contrasting with AZA-induced similar lesions which showed an abnormal ploidy. It remains to be established whether DNA phenotypic traits of NMU and AZA induced FACH reflect the neoplastic potentials of both types of lesions. The decreased number of tetraploid cells in EFAD rat pancreas is in keeping with data indicating a promoting effect of the EFA linoleic and arachidonic acids on growth rate of certain cell populations in vitro.