[Alkaline phosphatase activities in cultured human testicular embryonal carcinoma cells].

Several characteristics of alkaline phosphatases (ALP) in cultured embryonal carcinoma cells were studied by cytohistochemical and biochemical methods. The cell lines, ITO and NEC8, were derived from human testicular germ cell tumors. A few ALP-positive cells were found in the ITO cell line. Electronmicroscopically, small cells of yolk sac tumor type were positive for ALP. The activity was less heat-stable and more sensitive to Lhomoarginine than the late placental ALP, with a marked sensitivity to L-leucine. It was difficult to identify the activity with the well-known isoenzymes in the ITO line. Many ALP-positive cells were seen in the NEC8 cell line. The free-surface with microvilli of adult type embryonal carcinoma cells showed the most strong activity. The activity was heat-labile and markedly sensitive to L-homoarginine. The cell extract produced electrophoretically a band compatible to ALPS. These characteristics of the activity were similar to the early placental isoenzyme. The late placental isoenzyme was not detected in both the cell lines.