Arginase Activity, Ornithine and Urea Levels in Breast Cyst Fluid

Gross cystic disease of breast is the commonest benign disease of breast effecting1:20 women in the western world. There are two groups of breast cyst; lined eitherby metaplastic epithelium (Na/K<3) or flattened epithelium (Na/K>3). There isclear parallelism between their electrolyte ratios and epithelial characters. Severallarge studies have shown that the risk of breast cancer in women with gross cysticdisease to be 2 to 4,4 times higher and women with “apocrine” breast cyst mayhave a higher risk of developing breast cancer than women with breast cyst linedby flattened epithelium. Arginase, a cytoplasmic enzyme, catalyzes the hydrolysisof L-arjinine to urea and ornithine in the last step of the mammalian urea cycle.The most important function of arginase is the synthesis of urea. Arginase alsoplays an important role in the synthesis of polyamines through the ornithine. Theaim of the present study was to compare the distributions of arginase, ornithineand urea concentrations in breast cyst fluid in the 2 sub-groups of breast cyst.The possible roles which arginase, ornithine and urea may have on breast cancerdevelopment were investigated. Arginase enzyme activities, ornithine and urealevels were significantly higher in the apocrine cyst group. There was no differencein protein levels between the two cyst groups. In conclusion the finding of higharginase activity and ornithine levels in high risk breast cyst group the breast cystmay lead to an increase in the production of polyamines which were shown to betumor promoting agents, and thus may lead to development of breast cancer fromthe gross cystic breast disease.