title: Increased expression and activity of heme oxygenase-2 in pregnant rat aorta is not involved in attenuated vasopressin-induced contraction.
abstract: Pregnancy is associated with attenuated vascular reactivity to a variety of contractile agonists. Heme oxygenases are expressed in the placenta, and it has been suggested that the heme oxygenase/carbon monoxide (HO/CO) pathway plays a significant role in regulating blood flow through the feto-placental unit. In this study we investigated the possible involvement of heme oxygenases in the reduced vascular reactivity associated with pregnancy. Arginine vasopressin (AVP) (10(-10)-3x10(-7) M) induced concentration-dependent contraction of aortic ring segments from non-pregnant and pregnant (16-19 days) rats. Pregnancy did not alter the sensitivity to AVP (pD2=8.5+/-0.1 and pD2=8.4+/-0.2 in non-pregnant and pregnant rats, respectively) but significantly reduced the maximum response (107.9+/-12.7% and 38.6+/-7.4%, respectively, relative to noradrenaline-induced contraction). Western blot analysis revealed the expression of HO-2 but not HO-1 isoform in both groups. There was a significant increase in the expression and activity of HO-2 protein in aortic tissues from pregnant rats compared with those from age-matched non-pregnant rats. In the presence of L-NAME to inhibit nitric oxide (NO) synthesis, tin protoporphyrin IX (SnPP-IX, 10(-5) M), an inhibitor of heme oxygenase, did not significantly affect AVP-induced contraction in aorta segments from pregnant and non-pregnant rats. It was concluded that, though pregnancy increased the expression and activity of HO-2 in the aorta, HO-2 was not involved in the attenuated response to AVP.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Kuwait University, P.O. Box 24923, 13110, Safat, Kuwait.
authors.forename: Maram G
authors.initials: MG
authors.lastname: Katoue
authors.forename: Islam
authors.initials: I
authors.lastname: Khan
authors.forename: Mabayoje A
authors.initials: MA
authors.lastname: Oriowo
mesh_terms: D000818:Animals; D001011:Aorta; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology*; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014667:Vasopressins / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D014662:Vasoconstrictor Agents; D014667:Vasopressins; D011189:Potassium Chloride; D006419:Heme Oxygenase (Decyclizing); C105245:heme oxygenase-2; D019331:NG-Nitroarginine Methyl Ester