IMPORTANCE OF TYPE-IV COLLAGEN, LAMININ, AND HEPARAN-SULFATE PROTEOGLYCAN IN THE REGULATION OF LABYRINTHINE FLUID IN THE RAT COCHLEAR DUCT

The distribution of major components of the basement membrane, such as type IV collagen, laminin, and heparan sulfate proteoglycan (HSPG), w as investigated in the rat cochlear duct. Immunofluorescence demonstra ted that type IV collagen, laminin and HSPG were distributed along cap illaries in the cochlear duct, including the stria vascularis, spiral ligament, spiral prominence and spiral limbus. Additionally, type IV c ollagen, laminin and HSPG were found to be distributed from the baseme nt membrane of Reissner's membrane to that of the spiral prominence in a linear pattern. The scala media was surrounded by these basement me mbrane components, demarcating endolymph from perilymph, along epithel ial cells except at the stria vascularis. These findings suggest that type IV collagen, laminin and HSPG create the anatomical separation be tween endolymph and perilymph, thus indicating that they may be involv ed in the regulation of fluid transport between the endolymph and peri lymph.