title: The cardiovascular effects of porcine relaxin in Brattleboro rats.
abstract: The effects of porcine relaxin on arterial blood pressure, heart rate, and the release of vasopressin and oxytocin were investigated in homozygous diabetes insipidus (di/di) Brattleboro and Long-Evans rats. Acute iv injection of relaxin (5 microg) caused a significant increase in mean arterial, systolic and diastolic blood pressures in Long-Evans rats compared with control injections of saline, but had no pressor effect in Brattleboro rats. Circulating concentrations of vasopressin were also significantly elevated above baseline in the Long-Evans rats 1 min after relaxin treatment, but remained undetectable in the relaxin-treated Brattleboro rats. Relaxin increased heart rate in both groups of animals 4 min after injection. The chronotropic effect of relaxin was, however, attenuated in the Brattleboro rats. Intravenous relaxin injection also caused a significant increase in plasma oxytocin concentrations 5 min posttreatment in both the Long-Evans and Brattleboro rats. The change in plasma oxytocin above basal concentrations was significantly greater in Brattleboro rats compared with Long-Evans controls. The data in this study demonstrate that iv relaxin increases heart rate, but not arterial blood pressure in Brattleboro rats. Furthermore, the relaxin-induced release of oxytocin in Brattleboro rats does not result in an acute pressor response.
authors.affiliation: Department of Zoology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: L J
authors.initials: LJ
authors.lastname: Parry
authors.forename: B C
authors.initials: BC
authors.lastname: Wilson
authors.forename: R S
authors.initials: RS
authors.lastname: Poterski
authors.forename: A J
authors.initials: AJ
authors.lastname: Summerlee
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D010121:Oxytocin / Q000097:blood; D011863:Radioimmunoassay; D051381:Rats; D011910:Rats, Brattleboro; D012065:Relaxin / Q000494:pharmacology*; D013552:Swine; D014667:Vasopressins / Q000097:blood
chemical_list: D014667:Vasopressins; D010121:Oxytocin; D012065:Relaxin