Transepithelial potential difference

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The bioelectric, transepithelial potential difference (PD) is understood as a measurable electrical direct voltage ( millivolt range ) applied to epithelial or endothelial tissue .

It exists at the boundary layers of the body where fluids are exchanged between the inside and outside of the body (e.g. intestine, salivary glands) or two endo spaces (e.g. hemo- and sensillary lymph space) and the surfaces of the cells have direct contact with both. In the simplest case, such a boundary layer consists of a single-layer epithelium . In humans, no potential difference can be measured on the skin, which is keratinized to protect against external influences (see also multilayered squamous epithelium ); However, it can be detected in other multilayered squamous epithelia and frog skin.

Physiology / morphology

Each of the individual cells of such a surface layer has two fundamentally different areas:

  1. A part of the wall of a cell (which e.g. lies against the inside of the body) is structured like a typical cell membrane .
  2. However, the other part (e.g. that is in contact with the outside of the body) differs morphologically from it. It lacks the sodium-potassium pump and it is compared to the above-mentioned range for ions (in particular Na + , K + and Cl - ) is inversely permeable .

Therefore, the cause of changes in membrane potential is different in both areas.

There are basically two types of such surface layers:

  1. The "slightly permeable" (leaky); ions and water molecules can easily penetrate through the spaces between cells .
  2. The "impermeable" (tight); Ions and water molecules can hardly penetrate through the spaces between cells, the exchange takes place directly through the cells .

The characteristics, number and arrangement of the tight junctions are responsible for these differences . The cells in a layer communicate with one another directly via the gap junctions .

application

The potential difference is age-dependent. Changes can be used diagnostically. They reflect the functional status of the tight junctions and allow the effectiveness of drugs (e.g. non-steroidal anti-inflammatory drugs) to be assessed.

In the kidney , it is the transepithelial potential difference that enables paracellular chloride resorption.

In the respiratory tract , it allows the early diagnosis of cystic fibrosis .

swell

  1. ↑ H. Knauf, E. Frömter: Electrical investigations on the main duct of the salivary glands in humans . In: Pflüger's archive . tape 316 , no. 3-4 , September 1, 1970, pp. 238-258 , doi : 10.1007 / BF00586586 .
  2. ↑ Detection of pheromones in the silk moth's sensilla. (DOC) (No longer available online.) In: studentenlabor.de. Formerly in the original ; Retrieved November 14, 2007 .  ( Page no longer available , search in web archives )@1@ 2Template: Toter Link / www.studentenlabor.de
  3. ↑ a b Communication with the outside world. In: biologie-online.eu. Roman Boldt, accessed February 20, 2016 .
  4. ↑ Andreas Ziersch: Optimization of cystic fibrosis diagnostics and review of new therapeutic approaches based on nasal potential difference measurement . 1999, urn : nbn: de: hebis: 26-opus-2030 ( doctoral thesis [PDF; accessed on 19 September 2016]).
  5. ↑ a b James T. Blankemeyer, Sharif H. Shahin: Increase in Gap Junctions in Frog Skin Epithelium . In: Proceedings of the Oklahoma Academy of Science . tape 73 , 1993, pp. 23–27 ( digital.library.okstate.edu [PDF; 88 kB ]).
  6. ↑ N. Nicolaides, A. König, EH Ballke, B. Griefahn, K. Jahresig: The influence of acetylic acid on th transepithgelial potential difference of gastric mucosa in children. In: J. Molec. Med. 63, 2005, pp. 184-187.
  7. ^ BC Burkhardt: Lecture Kidneys, Salt and Water Balance ( Memento from July 15, 2007 in the Internet Archive )
  8. ↑ MR Knowles, JT Gatzy, RC Boucher: Increased bioelectric potential difference across respiratoy epithelia in cystic fibrosis. In: Engl. J. Med. 305, 1981, pp. 1489-1495.