[Effects of L-threonate on bone resorption by osteoclasts in vitro].

To clarify if calcium L-threonate and sodium L-threonate have inhibitory effects on the bone resorption of rabbit's osteoclasts in vitro.This study contained a total of 16 culture groups, including one group as control and 5 groups treated by 5 drugs (calcium D-threonate, sodium L-threonate, alendronate, 17beta-estradiol and calcium gluconate) each at the final concentrations of 10(-9) mol/L, 10(-7) mol/L, 10(-5) mol/L respectively. After 7 days, eight bone slices of every group were stained with toluidine blue and the areas of resorptive pits were analyzed under light microscope; the concentrations of C-telopeptide of type I collagen (CTx or Crosslaps) in culture supernatants were measured by ELISA.(1) The resorption area and the CTx concentration of the Calcium L-threonate groups were reduced significantly as compared with those of control and of Calcium gluconate groups respectively. The resorption area and CTx level of the Sodium L-threonate groups were significantly reduced when compared with those of the control, but the effects of Calcium gluconate groups were not so. (2) The reduction in the resorption area and CTx concentration of Calcium L-threonate group was more than that of Sodium L-threonate group. (3) The reductive effect of the high concentration (10(-5)) group of Calcium L-threonate on the area and CTx level was corresponding to that of 17beta-estradiol at a concentration between 10(-7) and 10(-9). (4) The resorption area was related to the CTx concentration (r=0.876). (5) The CTX level was much more sensitive, precise and stable than the concentration.L-threonate, especially calcium L-threonate could inhibit the bone resorption of osteoclasts in vitro, and its effect might be related to the radical of L-threonic acid. The CTx concentration in culture supernatants might be an effective marker quantitatively reflecting the bone resorption by osteoclasts in vitro.