Summary
These studies were intended to assess the osteogenic activity of monofluorophosphate (MFP)in vitro, and to identify the enzyme(s) responsible for MFP hydrolysis—alkaline phosphatase (ALP) and/or acid phosphatase (AcP). ALP and AcP activities were determined by hydrolysis of p-nitrophenylphosphate (PNPP) at pH>8 and pH 5.5, respectively, and MFP hydrolysis was determined, between pH 5.5 and pH 9.0, from measurements of [fluoride ion], using an ion-specific electrode. We found (1) that MFP was an alternative substrate for purified ALP, but not for AcP; (2) that MFPase activity in the embryonic chick resembled ALP, but not AcP, with respect to pH-dependent hydrolysis, sensitivity to effectors (r=0.98,P<.001), and tissue distribution (r=0.96,P <.001); and (3) that intestinal MFPase activity in the embryonic chick co-purified with ALP activity (r=0.93,P<.01) and resembled ALP, but not AcP, in its distribution along the small intestine, being highest in the duodenum and lowest in the distal ileum (r=0.96,P<.001). We also found thatin vitro exposure to MFP increased (1) the proliferation rate of embryonic chick calvarial cells in serum-free monolayer cultures (i.e.,3[H]-thymidine incorporation into DNA,P<.001); (2) ALP activity in calvarial cells (P<.005) and in intact calvaria (P<.05); and (3) collagen production by intact calvaria (i.e.,3[H]-proline incorporation as3[H]-hydroxyproline,P<.05). Together these data indicate that ALP, and not AcP, is responsible for MFP hydrolysis, and that MFP can mimic the osteogenic actions of NaF,in vitro.
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Farley, J.R., Tarbaux, N.M., William Lau, K.H. et al. Monofluorophosphate is hydrolyzed by alkaline phosphatase and mimics the actions of NaF on skeletal tissues,In Vitro . Calcif Tissue Int 40, 35–42 (1987). https://doi.org/10.1007/BF02555726
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DOI: https://doi.org/10.1007/BF02555726