Dark cell

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Dark cell
Anatomical terminology

Dark cells are specialized nonsensory

vestibular organs (the utricle and the ampullae of the semicircular canals[1]) and lining the endolymphatic space. These dark-cell areas in the vestibular organ are structures involved in the production of endolymph, an inner ear fluid, secreting potassium towards the endolymphatic fluid. Dark cells take part in fluid homeostasis to preserve the unique high-potassium and low-sodium content of the endolymph and also maintain the calcium homeostasis of the inner ear.[2]

Morphological and immunohistochemical studies in several species have indicated that these dark cell areas also form a single layer resting on top of pigmented cells at the base of the cristae ampullaris in the semi-circular canals and around the

utricular macula.[2]

Structure

Dark cells are morphologically and functionally similar to marginal cells of the stria vascularis as they both display characteristics of fluid transport tissue; however, studies indicate an earlier histological and immunohistological maturity in the dark-cell areas compared to the stria vascularis.[2]

The dark cell epithelium consists of cells with a multitude of pinocytotic vesicles near their luminal surface. A numerable portion of infoldings occurs at the basal end of the dark cell toward the basal membrane. These infoldings contain a high quantity of mitochondria. The nucleus of the dark cell is displaced toward the surface.[3]

Function

Vestibular dark cells transport

Na+/K+-ATPase pump in order to transport potassium.[4]

The

mitochondria, and they contain high levels of Na+/K+-ATPase in both alpha and beta isoforms, transporting potassium into the cell in exchange for sodium while consuming ATP.[5]
The infoldings also create large surface area over which ion exchange can take place and the plethora of mitochondria enclosed provides the needed energy source of ATP for active transport.

The basolateral membrane also contains a

ototoxic side effects through an action on the co-transporter in vestibular dark cells. These acute ototoxic side effects inhibit ion transport resulting in accumulation of ions in the extracellular space leading to edema.[7]

The apical membranes of the dark cells also have a K+ channel which is formed of two subunits, the

epithelia of the roof of the utricle, saccule and ampullae, as well as dysfunction of the vestibular sensory organs.[8]

Research

Many species (with recent studies done on dogs) are affected by balance disorders and hearing problems that can be caused by a problem in the dark-cell areas in the vestibular endorgans. Studies researching damaged dark cells due to genetic abnormalities or therapeutics are very important in attempting to understand the onset and mechanism of said balance impairments.[9]

Dogs have been used as models due to similarities between humans and dogs with regards to inner ear size, inner ear lesions and susceptibility to

ototoxins.[9]

See also

List of distinct cell types in the adult human body

References

  1. PMID 18570690
    .
  2. ^
    PMID 5305759
    .
  3. ^ Takumida, M (1999). "Vestibular Dark Cells and Supporting Cells". Science Links Japan. Archived from the original on 2013-08-08. Retrieved 8 August 2013.
  4. PMID 17005601
    .
  5. PMID 8014467
    .
  6. PMID 9199662
    .
  7. PMID 12324381
    .
  8. PMID 8982171
    .
  9. ^
    PMID 8456203
    .
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