Choriocarcinoma in Vitro: Evidence for Exchange of Enzymes Between Culture Medium and Cells

β-Glucuronidase and hexosaminidase isoenzyme patterns of choriocarcinoma in culture are similar to those of placenta. We present evidence for an exchange of enzymes between the culture medium and choriocarcinoma cells. The β-glucuronidase pattern for choriocarcinoma grown in medium supplemented with horse serum has a component, not found in placenta, with electrophoretic mobility identical to that of the single band of horse serum β-glucuronidase. Hexosaminidase activity in the culture medium removed was 40% higher than the medium added to the culture. The suggestion is made that the extra β-glucuronidase isoenzyme is derived from the serum supplement of the culture medium and that the increase in hexosaminidase activity in the medium removed from the culture is consistent with the release of this enzyme from the cells.