Characterization of alkaline phosphatase in human urinary bladder carcinoma cell lines and enzyme regulation with prednisolone or sodium chloride

Abstract

In order to characterize newly established human urinary bladder carcinoma cell lines (JTC-29, JTC-30, JTC-31, JTC-32, JTC-33 and JTC-34) by Kakuya et al. [In Vitro, 19, 591-599 (1983)], we investigated alkaline phosphatase in these cell lines. Relatively high alkaline phosphatase activity was found in JTC-29 and JTC-32 cells, but the enzyme activity in the other cell lines was very low. Prednisolone induced alkaline phosphatase activity even at 0.005 micrograms/ml (14 nM) and the effect was maximal at 0.05 micrograms/ml. NaCl also induced alkaline phosphatase activity at 50 mM. A further increase in the activity was observed at 0.1 M NaCl, but at 0.2 M all cells came off from plastic culture dishes without an increase in the enzyme activity during the incubation for 24 h at 37 degrees C. Both actinomycin D and cycloheximide abolished the increases in the enzyme activity with prednisolone or NaCl. The Lineweaver-Burk plot showed that the increases in the enzyme activity are due to the increases in Vmax, but not in Km. Alkaline phosphatase in JTC-32 cells and prednisolone-treated JTC-32 cells was heat stable and 100% of the initial enzyme activity remained after 30 min of incubation at 56 degrees C. However, the enzyme in JTC-29 cells was heat labile and its activity was reduced to less than 50% after 20 min of incubation at 56 degrees C. L-Phenylalanine was the strongest inhibitor for the enzyme reactions in JTC-32 cell homogenates among L-phenylalanine, L-leucine and L-homoarginine, whereas L-homoarginine was the strongest for the enzyme reactions in JTC-29 cell homogenates.(ABSTRACT TRUNCATED AT 250 WORDS)