Decreased responsiveness to noradrenaline, but not to diclofenac, of the growth-retarded guinea pig placental vasculature.
To examine vascular responsiveness of the growth-retarded placenta to noradrenaline and the cyclooxygenase inhibitor diclofenac, unilateral uterine artery ligation was carried out in 13 guinea pigs at 32 to 36 days gestation. Uteroplacental blood flows were measured with the microsphere technique at 49 to 52 days gestation in the chronically catheterized awake animal. During infusion of noradrenaline (1.5 nmol/min per kg) mean arterial blood pressure increased by 12% (P less than 0.001), placental blood flow in the normal-sized group decreased by 15% (P less than 0.01), while the growth-retarded placentas showed a different reactivity (P less than 0.001) in that an 8% increase in blood flow was observed. Diclofenac (1.5 mg/kg) caused small and statistically non-significant reductions in mean arterial blood pressure and blood flow to placentas of normal-sized and growth-retarded fetuses. It is concluded that the vessels supplying the growth-retarded placenta have a attenuated responsiveness to circulating noradrenaline and a delay in the pregnancy-induced sympathetic denervation is suggested as a mechanism. However, normal-sized and growth-retarded placentas did not differ in vascular response to inhibition of prostaglandin synthesis.
Jansson
T
T
Department of Physiology, University of Göteborg, Sweden.
D000818:Animals; D001158:Arteries; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight; D004008:Diclofenac / Q000494:pharmacology*; D005260:Female; D005317:Fetal Growth Retardation / Q000503:physiopathology*; D006168:Guinea Pigs; D008863:Microspheres; D009638:Norepinephrine / Q000494:pharmacology*; D009929:Organ Size; D010920:Placenta / Q000098:blood supply* / Q000187:drug effects / Q000503:physiopathology; D011247:Pregnancy; D012039:Regional Blood Flow; D014599:Uterus / Q000098:blood supply*
D004008:Diclofenac; D009638:Norepinephrine