Effect of pregnancy on vasopressin-mediated responses in guinea-pig uterine arteries with intact and denuded endothelium.
The effect of pregnancy on vasopressin-induced contraction of guinea-pig uterine arterial rings was investigated. Initially, vasopressin induced contraction (pD2 = 9.14) in pregnant guinea-pig uterine artery with greater potency than in non-pregnant guinea-pig uterine artery (pD2 = 8.77). Removal of the endothelium did not affect vasopressin-induced contractions, regardless of pregnancy status. In all types of preparations, [d(CH2)5Tyr(Me)2]vasopressin (10-100 nM) and [d(CH2)5,D-Ile2,Ile4]vasopressin (300 nM-3 microM) produced parallel rightward shifts of the curves for vasopressin. The Schild plots constrained to a slope of unity gave the following -log KB values: [d(CH2)5Tyr(Me)2]vasopressin vs. [d(CH2)5,D-Ile2,Ile4]vasopressin 8.74 vs. 6.82 and 8.50 vs. 6.72 for non-pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively; 8.38 vs. 6.49 and 8.36 vs. 6.75 for pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively. The pKA values for vasopressin itself also did not differs between preparations: 6.49 and 6.55 for non-pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively; 6.48 and 6.52 for pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively. The receptor reserve (KA/EC50) was significantly greater in preparations taken from pregnant than from non-pregnant animals. It is concluded that vasopressin-induced contractions of guinea-pig uterine artery are not modulated by the endothelium, regardless of pregnancy status. The receptor reserve for vasopressin in guinea-pig uterine artery is increased during pregnancy, that is not related to the changes of vasopressin receptor affinity for vasopressin. It is probable that vasopressin receptors involved in vasopressin-induced contraction of all types of vessels studied belong to the V1A-like subtype.
Jovanović
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A
Department of Pharmacology, Medical Faculty, Belgrade, Yugoslavia.
Grbović
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L
Jovanović
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S
Zikić
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I
D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D001158:Arteries / Q000187:drug effects; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D014599:Uterus / Q000098:blood supply* / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014667:Vasopressins / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D065092:Antidiuretic Hormone Receptor Antagonists; D014662:Vasoconstrictor Agents; D014667:Vasopressins