Abstract
The induction of alkaline phosphatase (ALP) by dibutyryl adenosine 3':5'-cyclic monophosphate (Bt2cAMP) was investigated in strain JTC-12•3 cells derived from monkey (Maccaca irus) kidney cortex. ALP activity was increased by Bt2cAMP in a dose-dependent manner, reaching a plateau at concentrations higher than 5mM with the activity being about 4 times that of the controls. The concentration of Bt2cAMP required for half-maximal induction of ALP activity was about 0.8mM. ALP activity was increased rapidly by Bt2cAMP for the first 5 days and then continued to increase gradually towards a plateau level. Removal of Bt2cAMP from the medium caused a rapid decrease in the activity, suggesting that the induction of ALP activity by Bt2cAMP is reversible. ALP activity was induced synergistically in the presence of 1mM sodium butyrate together with Bt2CAMP at concentrations from 0.01 to 1mM. It was also found that in the presence of 1mM Bt2cAMP, sodium butyrate increased ALP activity in the same manner as Bt2cAMP did in the presence of 1mM sodium butyrate. Although dexamethasone, a potent glucocorticoid, had no effect on ALP activity in control cells, the hormone suppressed the ALP activity induced by Bt2cAMP in a dose-dependent manner. At concentrations above 0.2mM, two xanthine derivatives, theophylline and 3-isobutyl-1-methyl-xanthine (IBMX), also inhibited the induction of ALP activity by 1mM Bt2cAMP. Inhibitors of protein synthesis, cycloheximide (1.5 μg/ml) and pactamycin (10 μg/ml), as well as inhibitors of RNA synthesis, actinomycin D (2 μg/ml) and α-amanitin (50 μg/ml), suppressed the induction of ALP activity. Hydroxyurea markedly enhanced the induction of ALP activity by 1mM Bt2cAMP in the range of dosages examined (5 to 80 μg/ml), while it did not cause any change in ALP activity in control cells. 5-Bromodeoxyuridine (BrdU) did not affect the level of ALP activity in control cells or in cells treated with I mNt Bt2cAMP. Thus, the level of ALP activity in JTC-12•3 cells was found to be influenced by several agents such as Bt2cAMP, sodium butyrate, dexamethasone, xanthine derivatives, and hydroxyurea.
