STEROID SULFOTRANSFERASE AND 17-BETA-HYDROXYSTEROID DEHYDROGENASE-ACTIVITIES IN ISHIKAWA HUMAN ENDOMETRIAL ADENOCARCINOMA CELLS

The present studies concern sulphotransferase activities for estrogens and other steroids, and 17 beta-hydroxysteroid dehydrogenase (17 beta -HSD) activities for estrogens in Ishikawa endometrial adenocarcinoma cells. When physiological concentrations of various estrogens (estrone , estradiol, estriol) are incubated, most of the transformation produc t is the respective sulphate. The sulphotransferase activity is very r apid, and 2 h after incubation 70-95% are converted to the sulphated f orm. Sulphates are found exclusively in the culture medium, which sugg ests that as soon as the sulphate is biosynthesized it is secreted to the medium. Comparative data using neutral steroids (dehydroepiandrost erone, testosterone, and pregnenolone) show that sulphotransferase act ivity for these compounds is very limited. In another series of studie s, 17 beta-HSD activity was explored for the interconversion estrone < -> estradiol. At low concentrations (5 x 10(-9)-5 x 10(-8) M), when es tradiol (E-2) is incubated, most of the unconjugated material remains as E-2 in the cellular compartment, but at high concentrations (5 x 10 (-7)-5 x 10(-6) M) a great proportion (70-80%) of the E-2 is converted to estrone (E-1). On the other hand, after incubation of E-1 at all c oncentrations most remained as unchanged E-1. It is suggested that, in Ishikawa cells, at very low concentrations of E-1 or E-2, sulphotrans ferases are predominant, but when this enzyme is saturated 17 beta-HSD activity is orientated to the oxidative form. (C) 1997 Elsevier Scien ce Ltd.