title: Release of an oxytocic peptide at parturition in the marsupial, Macropus eugenii.
abstract: The oxytocic peptide mesotocin was measured in plasma samples collected throughout pregnancy in the conscious tammar wallaby, Macropus eugenii. Plasma mesotocin and the prostaglandin metabolite 13,14-dihydro-15-oxo-prostaglandin F2 alpha were also assessed immediately prepartum and during parturition. A radioimmunoassay for mesotocin was validated in the tammar and this assay allowed direct measurement in 50 microliters unextracted plasma with a sensitivity of 12.5 pmol l-1. Plasma concentrations of mesotocin remained basal (approximately 15 pmol l-1) at all stages of pregnancy, including prepartum. A significant (P < 0.05) increase in plasma mesotocin was observed only immediately after delivery of the neonate and this increase was maintained for at least 15 min postpartum. Mesotocin concentrations returned to basal values 2 h after birth. Peak concentrations of mesotocin of 516.7 +/- 108.1 pmol l-1 were measured within 2 min of birth. This peak coincided with a short-lived peak in concentration of prostaglandin F2 alpha metabolite immediately after birth (2.1 +/- 0.4 nmol l-1) which decreased to less than 0.3 nmol l-1 within 2 h postpartum. These data demonstrate that mesotocin is released during, or immediately after, delivery and appears to parallel the profile of circulating prostaglandin F2 alpha metabolite in this marsupial.
authors.affiliation: Department of Zoology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: L J
authors.initials: LJ
authors.lastname: Parry
authors.forename: F J
authors.initials: FJ
authors.lastname: Guymer
authors.forename: T P
authors.initials: TP
authors.lastname: Fletcher
authors.forename: M B
authors.initials: MB
authors.lastname: Renfree
mesh_terms: D000818:Animals; D015237:Dinoprost / Q000031:analogs & derivatives / Q000097:blood; D005260:Female; D007743:Labor, Obstetric / Q000097:blood; D007614:Macropodidae / Q000502:physiology*; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D049590:Postpartum Period / Q000097:blood; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D011863:Radioimmunoassay
chemical_list: C008228:15-keto-13,14-dihydroprostaglandin F2alpha; C001713:mesotocin; D010121:Oxytocin; D015237:Dinoprost