Publication: Morphological aspects of potassium flow in the semicircular canal ampulla of the pigeon
Authors
Helling, K. ; Merker, H. J.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
Potassium ions are a prerequisite for the
development and regulation of sensory cell stimulation
in the inner ear. From the potassium-rich endolymph the
ions flow into the sensory cells apically and are released
basolaterally. After transport pathways of various
lengths potassium is released again into the endolymph -
in the cochlea by marginal cells of the stria vascularis, in
the vestibular labyrinth by dark cells. While this long
recycling pathway is relatively well-known in the
cochlea, few studies have been conducted on the
semicircular canal ampullae (SCCA) where its
morphological basis is largely unknown.
According to the present electron microscopic
findings, potassium ions are initially released into the
extracellular space during stimulation of the sensory
cells and then absorbed by supporting and light cells.
Finally they are transported transcellularly over
numerous very long gap junctions into the region of the
dark cells. From here they move to an extracellular
compartment, which is more or less completely sealed
off basally by basal plates of the light cells. Apically the
intercellular space between light and dark cells is sealed
by junctional complexes. This newly identified space in
the SCCA corresponds to the extracellular compartment
between the marginal and intermediate cells in the stria
vascularis. At both sites, the cochlea and the SCCA, this probably serves as a regulatory valve, reservoir or
storage space, particularly for potassium ions. It is likely
that the different morphology of the ion transport
pathways is related to the different flow levels of
potassium ions expressed by the different levels of the
so-called endocochlear potential and concomitant
movement of other ions in the cochlea and SCCA.
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