Inhibin
Inhibin is a - in the human body - as a glycoprotein formed proteohormone which in the Sertoli cells of the testis and in the granulosa cells of the ovary is formed. It regulates the release of FSH : The release of inhibin is stimulated by FSH, at the same time it inhibits its release from the pituitary gland . It is named after the inhibition of FSH formation in the pituitary gland. The substance inhibin was postulated by McCullagh in 1932, but it was not until 1985 that it was isolated and characterized.
Inhibin consists of two protein chains, an alpha and a beta chain. Since there are several different beta chains (beta-A and beta-B), several different inhibins can be formed: for example inhibin A (from an alpha and beta-A chain) or inhibin B (from an alpha and a beta-B chain). Inhibin A occurs mainly in the ovaries, inhibin B in the testes (see above).
The genes coding for the subunits are INHA , INHBA , INHBB , INHBC and INHBE .
As a special feature in the group of protein hormones, two beta chains can also combine and then form a hormone called activin , which, unlike inhibin, does not inhibit FSH, but stimulates its release from the pituitary gland. Depending on the chain composition, there is therefore Activin A (two Beta-A chains), Activin B (two Beta-B chains) and Activin AB (Beta-A and Beta-B chains). The first description was made at the same time by two working groups working on different floors of the Salk Institute in La Jolla, California, and who published their discovery in the same issue of the journal Nature . In the cited article, N. Ling's working group coined the term Activin because of its FSH-stimulating effect.
In addition to the better known activin subunits (beta chains), Activin beta A beta and activin B were in mammals described further 2 subunits (activin beta C and activin beta E), which both homo- and hetero- dimers can be formed. Their physiological function is still largely unclear. In Xenopus laevis also still activin beta D described.
In addition, hormones from the group of inhibins are also formed in other animal and plant organisms. Because of the high degree of conservation between the species, it can be assumed that inhibin and activin are important hormones not only for sexual function. They also play a role in the cell division of Xenopus laevis.
Inhibin should not be confused with the antimicrobial inhibins (e.g. in honey ).
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- ^ DR McCullagh: Dual endocrine activity of the testes. In: Science. 76, 1932, pp. 19-20. PMID 17815236
- ↑ N. Ling, SY Ying, N. Ueno et al .: Isolation and partial characterization of a Mr 32,000 protein with inhibin activity from porcine follicular fluid. In: Proc Natl Acad Sci. 82, 1985, pp. 7217-7221. PMID 3864157
- ↑ W. Vale , J. Rivier, J. Vaughan et al .: Purification and characterization of an FSH releasing protein from procine ovarian follicular fluid. In: Nature. 321, 1986, pp. 776-779. PMID 3012369
- ↑ N. Ling, SY Ying, N. Ueno et al: Pituitary FSH is released by a heterodimer of the beta subunits from the two forms of inhibin. In: Nature. 321, 1986, pp. 779-782. PMID 3086749
- ↑ A. Deli, E. Kreidl et al: Activins and activin antagonists in hepatocellular carcinoma. In: World J Gastroenterol. 14 (11), Mar 21, 2008, pp. 1699-1709. PMID 18350601