Esterase activity in human breast cyst fluid: associations with steroid sulfates and cations.

Human breast cyst fluid (BCF) contains an esterase that on the basis of electrophoretic mobility and response to inhibitors differs from those found in the plasma. From a total of 384 BCF samples analyzed for esterase using p-nitrophenyl hexanoate as substrate, 149 (39%) showed significant activity. The samples had been analyzed for the concentrations of the sulfates of estrone, estriol, dehydroepiandrosterone, as well as the potassium and sodium cations (K+/Na+). The data were submitted to statistical analysis using the Spearman rank order test. The esterase-positive samples exhibited a significant positive association with each of the steroid sulfates and the K+/Na+ ratios. Except for protein concentration, there was no significant correlation between the esterase-positive and esterase-negative cysts. These observations may have physiological significance in that high K+/Na+ ratio cysts have been related to the histological status of the cyst.