DEVELOPMENT OF INTRACELLULAR CA-ATPASE IN THE GERBIL OUTER HAIR CELL LATERAL WALL

The development of Ca-ATPase immunoreactivity in gerbil outer hair cel ls (OHCs), assayed by immunofluorescence and postembedding immunocytoc hemistry, is reported here. In the adult, a linear array of label is s een inside the lateral plasma membrane. The ultrastructural distributi on of Ca-ATPase near the OHC lateral plasma membrane was examined usin g immunogold cytochemistry and showed this calcium pumping enzyme to b e present throughout the subsurface cisternal complex (SSC), especiall y near the innermost layers. During development, Ca-ATPase immunoreact ivity appeared in patches near the lateral plasma membrane of some OHC s of the third row by 12 days after birth (DAB). By 15-16 DAB, punctat e immunoreactivity was detected in the second and first rows. At 20 DA B, immunostaining near OHC lateral plasma membrane was increased. but was less continuous than OHC staining in the adult cochlea. The appear ance of Ca-ATPase in OHCs coincides with the onset of auditory functio n and isolated OHC motility in the gerbil. The ultrastructural demonst ration of abundant sites of calcium pumps in the SSC supports a role f or this structure in the intracellular storage of calcium. These findi ngs suggest a possible role of Ca-ATPase and the SSC in the regulation of slow motility of OHCs which has been reported to depend on intrace llular calcium concentration.