Lack of Promoting Effects of α‐Linolenic, Linoleic or Palmitic Acid on Urinary Bladder Carcinogenesis in Rats

Potential promoting effects of α‐linolenic, linoleic and palmitic acids were investigated in a two‐stage urinary bladder carcinogenesis model. In experiment 1, male F344 rats were given 0.05% N‐butyl‐N‐(4‐hydroxybutyl)nitrosainine (BBN) in their drinking water for 4 weeks and then basal diet containing 10%α‐linolenic, 10% linoleic or 10% palmitic acid along with 0.2% butylated hydroxyanisole (BHA) as an antioxidant for 24 weeks. The development of tumors in the urinary bladder was not increased by treatment with any of the fatty acids. In experiment 2, male F344 rats were given 10%α‐linolenic, 10% linoleic or 10% palmitic acid along with 0.2% BHA in their diet for 8 weeks without prior BBN treatment. The administration of fatty acids was not associated with any increase in the 5‐bromo‐2′‐deoxyuridine labeling index of the urinary bladder epithelium. Serum and/or urine fatty acid Ievels increased in the cases of α‐linolenic and linoleic acid treatments, but not with palmitic acid. Under the present experimental conditions neither the two polyunsaturated nor the one saturated fatty acid exerted any promoting effect on urinary bladder carcinogenesis.