oxytocin(redirected from Ocytocin)
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(also pitocin), a hormone that is produced by the neurosecretory cells of the anterior nuclei of the hypothalamus. Oxytocin is transported over nerve fibers from the hypothalamus to the posterior lobe of the hypophysis, where it accumulates and is then released into the blood. It elicits contractions of the smooth muscles of the uterus and, to a lesser degree, the muscles of the urinary bladder and intestine. It also stimulates the flow of milk from the mammary glands. Oxytocin is secreted in response to stimulation of the nipple during lactation and distention of the uterus in the late stages of pregnancy. Adrenaline suppresses the secretion of oxytocin, and progesterone counteracts oxytocin’s effect on the uterine muscles.
Oxytocin is an octapeptide Whose four amino-acid groups are bound in a ring by cystine, which is also linked to a tripeptide:
Oxytocin—which is structurally similar to the other hypophyseal hormone, vasopressin—was isolated in pure form from biological substances (1950) and produced synthetically (1954) by V. du Vigneaud and co-workers; this was the first synthesis of a biologically active protein. A less expensive, synthetic oxytocin is used in medicine.
V. M. SAMSONOVA