Novel structures in marginal and intermediate cells presumably relate to functions of apical versus basal strial strata.
Prior ultrastructural studies showed that K+ supplied to the stria vascularis came from recycling ions from the organ of Corti or perilymph to strial basal cells. A newly distinguished basal subtype of intermediate cell (BIC) completely covered the basal cells with a leaf-like horizontal process and appeared situated to absorb from them all of the recycled K+. The basal region of marginal cells (MCs) projected foot-like and enlarged processes to border BICs opposite an unique ca. 150 angstroms space. These basal MC processes appeared positioned to resorb part of the K+ recycled to BICs. A second, upper subtype of IC (UIC), occupying middle to upper strial strata, contacted BIC's extensively. UICs were thus located to resorb from BICs the portion of the recycled K+ not forwarded to basal MC processes. The apical segment of MCs projected mitochondria-filled primary processes and numerous associated secondary processes. The Na,K-ATPase-rich secondary processes populated mid to upper stria where they could siphon K+ from UICs and resorb and secrete the ions thus generating the 150 mM [KCl] of endolymph. The morphologic relationship of basal marginal cell processes to BICs differed so strikingly from the relation of upper MC processes to UICs as to suggest a different function for basal stria, one possibly concerned with generating the endocochlear potential.
Spicer
Samuel S
SS
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 165 Ashley Avenue, Suite 309, P.O. Box 250908, Charleston, SC 29425, USA.
Schulte
Bradley A
BA
D000818:Animals; D005849:Gerbillinae / Q000033:anatomy & histology / Q000378:metabolism; D017136:Ion Transport; D008854:Microscopy, Electron; D008954:Models, Biological; D011188:Potassium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013316:Stria Vascularis / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure*
D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium