Quantification of osteoclastic resorption of the bovine otic capsule in vitro by an enzyme-linked immunosorbent assay

The bony shell surrounding the inner ear is known to have a very pronounced centripetal inhibition of remodelling in vivo, with almost no bone turnove r immediately adjacent to the perilymphatic spaces and a gradually increasi ng turnover rate towards outer parts of the bony otic capsule, By the use o f in vitro markers of bone resorption, including an enzyme-linked immunosor bent assay for quantification of type I collagen degradation and a colorime tric enzyme assay for quantification of osteoclast tartrate-resistant acid phosphatase activity, this study demonstrates that there are no ex vivo dif ferences in bone matrix resorption between the inner and outer parts of the otic capsule when exposed to seeded osteoclasts from rabbits. Thus, the un ique spatial distribution of perilabyrinthine bone turnover is not caused b y a shift in resorbability from inner to outer capsular bone that is due to inherent bone quality differences particular to these bone compartments. M ore likely, the sustained action of some intravital 'field force', originat ing from the inner ear spaces, is responsible for the unique spatial distri bution of the otic capsular bone turnover found in vivo. Though the charact er of this force is not yet defined, it is appealing to relate it to the la rge electromagnetic potential gradient present in the inner ear. Copyright (C) 2000 S. Karger AG, Basel.