EFFECT OF OUTER-MEMBRANE OF TREPONEMA-DENTICOLA ON BONE-RESORPTION

The effect of the outer membrane (outer sheath) of Treponema denticola on bone resorption was studied. Bone resorption was measured by the r elease of previously incorporated Ca-45 from the shafts of the radii a nd ulnae of 19-day fetal rats. A treated-over-control ratio (T/C ratio ) significantly greater than 1 indicated the stimulation of bone resor ption by the test substance. The addition of outer membrane of T denti cola increased the release of Ca-45 from the assay bones. The minimum concentrations required to yield significant Ca-45 release from the as say bones were 15, 22 and 75 mug protein/ml for serovars a, b and c, r espectively. These protein values corresponded to estimated lipopolysa ccharide contents of 0.6, 0.8 and 2.8 mug/ml, based on 3-deoxy-2-manno -octulosonate analysis. Heat treatment of outer membrane (60-degrees f or 30 min) did not change the effect on Ca-45 release. Parathyroid hor mone or prostaglandin E2, known to act synergistically with lipopolysa ccharides in bone resorption, was also added to the assay system. Neit her prostaglandin E2 at 10(-7) M nor parathyroid hormone at 40 ng/ml, by itself, increased Ca-45 release. However, in the presence of 10 mug protein/ml of outer membrane of serovar b at 120 h, the T/C ratio was increased to 1.31 +/- 0.07 and 1.58 +/- 0.118, respectively. These re sults suggest that a lipopolysaccharide-like material is present in th e outer membrane of T denticola that may be responsible for bone resor ption in the in vitro system.