Окситоцин

Oxytocin is a peptide hormone containing nine amino acids secreted and synthesized by the paraventricular and supraoptic nuclei of the hypothalamus and stored and released by the neurohypophysis. It acts in females by inducing uterine contractions during parturition and stimulating milk ejection by the mammary glands. No actions in males are known. Synthetic derivatives of oxytocin are used to induce labor and for therapeutic abortions. In recent years the safety of oxytocin has been greatly enhanced by the use of continuous maternal and fetal monitoring and by the use of controlled intravenous infusion of the drug.

Oxytocin is a white to yellowish brown powder, hygroscopic, easily soluble in water. It is a synthetic cyclic nonapeptide having the structure of the hormone produced by the posterior lobe of the pituitary gland that stimulates contraction of the uterus and milk ejection in receptive mammals.

ChEBI: Oxytocin is a cyclic nonapeptide hormone with amino acid sequence CYIQNCPLG that also acts as a neurotransmitter in the brain; the principal uterine-contracting and milk-ejecting hormone of the posterior pituitary. Together with the neuropeptide vasopressin, it is believed to influence social cognition and behaviour. It has a role as an oxytocic and a vasodilator agent. It is a peptide hormone and a heterodetic cyclic peptide.

Oxytocin is a cyclic nonapeptide that differs from vasopressin by only 2 amino acids. It is synthesized as a larger precursor molecule in cell bodies of the paraventricular nucleus, and to a lesser extent, the supraoptic nucleus in the hypothalamus. The precursor is rapidly converted by proteolysis to the active hormone and its neurophysin, packaged into secretory granules as an oxytocin-neurophysin complex, and secreted from nerve endings that terminate primarily in the posterior pituitary gland. In addition, oxytocinergic neurons that regulate the autonomic nervous system project to regions of the hypothalamus, brainstem, and spinal cord. Other sites of oxytocin synthesis include the luteal cells of the ovary, the endometrium, and the placenta.

Oxytocin (OXT) is a potent natriuretic hormone encoded by the gene mapped to human chromosome 20p13. It is synthesized along with its carrier protein neurophysin I from its inactive precursor prepro-OXT. OXT gene consists of three exons and two introns, where first exon codes for hormone OXT while other exon codes for neurophysin I.

Uterine contraction, milk ejection, facilitates sperm ascent in female tract
Decreases membrane potential of myometrium, basic metabolic rate, and liver glycogen
Stimulates oviposition in hen, releases luteinizing hormone (LH)
Increases blood sugar and urinary sodium and potassium

Poison by intravenous route. Experimental reproductive effects. Oxytocin is a pituitary hormone which stimulates uterine contraction and milk production. The principal uterus-contracting and lactation-stimulating hormone of the posterior pituitary gland.

It is a cyclic nonapeptide which is purified by countercurrent distribution between solvent and buffer. It is soluble in H2O, n-BuOH and isoBuOH. [Bodanszky & du Vigneaud J Am Chem Soc 81 2504 1959, Cash et al. J Med Pharm Chem 5 413 1962, Sakakibara et al. Bull Chem Soc Jpn 38 120 1965; solid phase synthesis: Bayer & Hagenmyer Tetrahedron Lett 2037 1968.] It was also synthesised on a solid phase matrix and finally purified as follows: A Sephadex G-25 column is equilibrated with the aqueous phase of a mixture of 3.5% AcOH (containing 1.5% of pyridine)/n-BuOH/*C6H6 (2:1:1) and then the organic phase of this mixture is run through. A solution of oxytocin (100mg) in H2O (2mL) is applied to the column which is then eluted with the organic layer of the above mixture. The fractions containing the major peak [as determined by the Folin-Lowry protein assay: Fryer et al. Anal Biochem 153 262 1986] are pooled, diluted with twice their volume of H2O, evaporated to a small volume and lyophilised to give oxytocin as a pure white powder (20mg, 508 U/mg). [Ives Can J Chem 46 2318 1968, Beilstein 22 III/IV 82.]