Effect of nitric oxide synthase inhibition on the uterine vasculature of the late-pregnant ewe.
OBJECTIVE
We studied the role of nitric oxide in the maintenance of uterine vascular tone during pregnancy.


METHODS
Late-pregnant ewes were instrumented with ultrasonographic flow probes on the left and right main uterine arteries. A catheter was passed retrogradely into 1 uterine artery from a tributary. In 14 animals nitric oxide synthase inhibitor (N omega-nitro-L-arginine methyl ester; L-NAME) was infused at 2 or 20 mg/kg during a 1-minute period into either the main left or right uterine artery.


RESULTS
The nitric oxide synthase inhibitor (20 mg/kg), infused into 1 uterine artery, significantly decreased uterine blood flow (P <.001) bilaterally, increased (P <.05) mean arterial pressure, and decreased heart rate (P <.05). The compound (when infused at 2 mg/kg) also significantly (P <.05) decreased uterine blood flow in the artery ipsilateral to, but not contralateral to, the infusion, with no change in mean arterial pressure and a decrease (P <.05) in heart rate.


CONCLUSIONS
During ovine pregnancy, endogenous nitric oxide production contributes to uterine vasodilatation.
D000818:Animals; D001158:Arteries / Q000187:drug effects; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005865:Gestational Age; D007261:Infusions, Intra-Arterial; D007700:Kinetics; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D011247:Pregnancy; D012756:Sheep; D014599:Uterus / Q000098:blood supply*; D014655:Vascular Resistance / Q000187:drug effects