Sialic acid metabolism in rats undergoing chemically induced hepatocarcinogenesis in specific dietary states

The sialic acid content and the activities of the enzymes responsible for the activation, transfer, and hydrolysis of sialic acid were determined in the livers of male Sprague-Dawley rats maintained on diets containing the hepatocarcinogen 2-acetylaminofluorene (AAF). The incidence of hyperplastic lesions was modulated by dietary fat and by the presence of a synthetic antioxidant. The purified diets utilized differed in the amount and degree of unsaturation of the lipid component; they contained either 20% corn oil, 18% coconut oil + 2% linoleic acid, or only 2% linoleic acid, and each diet was prepared either with or without 0.3% butylated hydroxytoluene (BHT). The supplementation of diets with BHT greatly retarded the development of hyperplastic nodules compared to unsupplemented diets. The AAF-treated rats and age-matched controls fed AAF-free diets were killed after a 12 to 17-week period of dietary treatment, and the livers were removed for histological and biochemical studies. Significant increases in sialic acid content, and in the activities of CMP-sialic acid synthetase and neuraminidase were observed in the livers from AAF-treated rats. The BHT supplementation of the AAF-containing diets resulted in livers with lower levels of sialic acid and CMP-sialic acid synthetase activities. The chemical and enzymatic changes observed in AAF-treated rats are consistent with an increased turnover of sialoglycoconjugates during the carcinogenic process.