Monofluorophosphate is hydrolyzed by alkaline phosphatase and mimics the actions of NaF on skeletal tissues, in vitro.

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 greater than 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 less than .001), and tissue distribution (r = 0.96, P less than .001); and (3) that intestinal MFPase activity in the embryonic chick co-purified with ALP activity (r = 0.93, P less than .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 less than .001). We also found that in 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 less than .001); (2) ALP activity in calvarial cells (P less than .005) and in intact calvaria (P less than .05); and (3) collagen production by intact calvaria (i.e., 3[H]-proline incorporation as 3[H]-hydroxyproline, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)