Nitric oxide regulates ovarian blood flow in the rat during the periovulatory period.
BACKGROUND
The aim of this study was to characterize the roles of nitric oxide (NO) on the rat ovarian blood flow (OBF) during the preovulatory period.


RESULTS
Immature Sprague-Dawley rats were primed with pregnant mares' serum gonadotrophin (PMSG, 15 IU) and given hCG (15 IU) 48 h later. The ovary was exposed 48-56 h after PMSG, a laser Doppler probe was attached to the ovarian surface and OBF was measured at two time periods: preovulatory (PO) 48 h after PMSG and ovulatory (OV) 6-8 h after hCG. A non-selective NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), was injected i.v. (4 and 10 mg/kg) or intrabursally (1 mg/kg). Intravenous administration of L-NAME to OV rats rapidly increased blood pressure and reduced OBF by 30%, which returned to the pretreatment level within 30 min. L-NAME given into the ovarian bursa of both PO and OV rats did not affect blood pressure and reduced OBF by nearly 40%, which remained low throughout the experiment. Intravenous injection of hCG to PO rats increased OBF to 116.1% at 5 min and 133.5% at 30 min in relation to the pretreatment level. When L-NAME was given intrabursally, subsequent hCG injection was without effect.


CONCLUSIONS
These results indicate that locally produced NO is important for the maintenance and increase of rat OBF during the preovulatory period.
D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D006063:Chorionic Gonadotropin / Q000008:administration & dosage; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006064:Gonadotropins, Equine / Q000008:administration & dosage; D007275:Injections, Intravenous; D017078:Laser-Doppler Flowmetry; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010053:Ovary / Q000098:blood supply* / Q000187:drug effects; D010060:Ovulation; D051381:Rats; D017207:Rats, Sprague-Dawley
D006063:Chorionic Gonadotropin; D004791:Enzyme Inhibitors; D006064:Gonadotropins, Equine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester