Immunocytochemical localization of contractile and contraction associated proteins in the spiral ligament of the cochlea.

Most of the extracellular fibers of the spiral ligament are associated with a distinct band of 'anchoring' cells which occur at the boundary between the spiral ligament and the otic capsule. These cells are characterized by parallel arrays of intracellular filaments which, along with the extracellular fibers, insert into electron dense, conical adhesion plaques. The intracellular filaments show a close morphological resemblance to the 'stress fibers' of cultured fibroblasts (Henson et al., 1984). In the present study we have demonstrated by immunofluorescence techniques that the anchoring cells, unlike adjacent cells of the spiral ligament, contain a complement of proteins that is typically associated with stress fibers and with contractile systems. In addition to actin, the cells contain myosin, tropomyosin, alpha-actinin and talin. These results lend further support to the hypothesis that the anchoring cells have the capacity to create and/or maintain tension on the spiral ligament-basilar membrane complex and to influence the mechanical properties of the basilar membrane.