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ACTH is secreted from the pituitary into the peripheral circulation and is critical for the maintenance of adrenocortical function and cortisol secretion. In the anterior pituitary, POMC is processed predominantly to adrenocorticotropin (ACTH) and β-lipotropin (β-LPH), but some β-endorphin is also produced. The posttranslational processing of POMC is tissue specific and results in the production of peptides with very different biological activities. POMC is synthesized independently in the anterior and intermediate lobes of the pituitary gland, in the brain, and in several peripheral tissues, including the gastrointestinal tract, reproductive tract, placenta, and cells of the immune system. The other two classes are composed of the enkephalins and the dynorphins, which are derived from separate precursor proteins. β-Endorphin is one of the three major classes of endogenous opioid peptides. Β-Endorphin is a 31-amino-acid peptide that is derived from the larger molecular weight precursor protein proopiomelanocortin (POMC). Wardlaw, in Encyclopedia of Stress (Second Edition), 2007 Structure, Synthesis, and Localization However, the in vivo studies are not completely confirmatory as it is well known that β-endorphin is rapidly metabolized in the plasma and that other bioactive peptides may yield high affinity to opioid receptors and confer the function. 1 Nonhuman primate studies in which β-endorphin is injected intravenously reported that this peptide most probably acts at mu receptors on the hypothalamus.
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18 In vivo studies of the function of β-endorphin at mu opioid receptors suggest that prolactin release after systemic injections mediate many of the neuroendocrine responses. Consequently, the classic effects of mu receptors including confirmation of analgesia and respiratory depression are not attributed to the endogenous peptide β-endorphin. Some studies suggest that β-endorphin has few central nervous system mediated effects when administered systemically because of the inherent difficulty for β-endorphin to cross the blood–brain barrier. Β-Endorphin serves as an agonist for mu opioid receptors and in vitro and in vivo studies have supported its function at these receptors to be neuroendocrine or neuroimmune in nature. Zagon, in Handbook of Biologically Active Peptides (Second Edition), 2013 β-Endorphin and Mu Receptor Functions They were ascribed to the C-terminal tetrapeptide region of β-endorphin.
![beta-endorphin beta-endorphin](https://image.shutterstock.com/image-illustration/beta-endorphin-chemical-formula-science-600w-1692693886.jpg)
These actions may represent a modulation by β-endorphin of the immune system in stress situations.
![beta-endorphin beta-endorphin](https://www.imago-images.de/bild/st/0103750843/w.jpg)
It binds to components of human complement and thymoma cells and stimulates the proliferation of lymphocytes. Various nonopiate actions of human β-endorphin on the immune system have been reported. Β-Endorphin is released from the pituitary into the blood under physical and emotional stress. Together these observations indicate an important role for β-endorphin in the insulin-independent uptake of glucose during exercise. Its effect on glucose uptake was mediated partly via a ∂-opioid receptor. β-Endorphin itself was more potent in increasing glucose uptake in contracting muscles than noncontracting muscles. In addition β-endorphin, glycylglutamine, and the MPF analog stimulated glucose uptake in isolated skeletal muscles. Furthermore, β-endorphin can be released by electrical stimulation of motoneurons, and POMC mRNA is upregulated in vivo in chronically stimulated motoneurons. β-Endorphin, glycylglutamine, and the MPF analog also reduced fatigue in isolated muscles stimulated at high frequency via the motor nerve. β-Endorphin(1–31), β-endorphin(1–27), glycylglutamine, and the stabilized synthetic melanotrophin-potentiating factor (MPF) analog, N-acetyl-Lys-D-Lys-Sar-Glu, all increased the contractile response in isolated muscles of the rat. Plasma β-endorphin has a number of actions on the periphery during exercise.
#Beta endorphin pro#
It has been reported to mediate the euphoria experienced in pro longed exercise and to inhibit postexercise pain. Β-Endorphin is released from the pituitary into the blood during stress and exercise. SMITH, in Handbook of Biologically Active Peptides, 2006 Exercise and Stress