α1-Antichymotrypsin complexes in human breast cyst fluids

Alpha(1)-antichymotrypsin, a serum protease inhibitor, was found in 72 breast cyst fluids aspirated from women affected by gross cystic breast disease. When fractionated by gel chromatography, the presence of protein complexes or aggregates was demonstrated. A different distribution of the alpha(1)-antichymotrypsin appeared to be related to the ionic composition of the breast cyst fluid; when compared with metabolically active apocrine cysts, a statistically significant increase of alpha(1) protease inhibitor values in flattened epithelial cysts was revealed (P < 0.001). Two-dimensional immunoelectrophoresis showed in apocrine cysts (Na/K ratio < 3) a characteristic double peak of alpha(1)-antichymotrypsin immunoprecipitin curve. The relationship between this alpha(1) protease inhibitor and electrolyte profiles may provide further knowledge about the imbalance between proteases and their inhibitors on functional changes of gross cysts and might be useful in studies on their mechanism of formation and relationship to subsequent breast cancer.