Influence of nitric oxide on the blood flow in the porcine uterine artery; an in vivo study.

The aim of this study was to investigate the role of nitric oxide (NO) in the regulation of blood flow in the porcine uterine artery during the course of the oestrous cycle. Experiments were carried out on animals on days 1-5, 8-13 and 17-20 of the oestrous cycle. After induction of anesthesia and opening of the abdominal cavity, blood samples were collected from the ovarian and uterine arteries and veins to determine nitrate and nitrite concentrations; on the opposite side to the blood sampling the branch of the uterine artery was prepared and a venous catheter was inserted into the artery. For measuring the changes in the blood pressure the catheter was connected via a polyvinyl cannula to a pressure transducer. Sodium nitroprusside (NP; 2.4 microg, 24 microg and 240 microg; a NO donor) or Nomega-nitro-L-arginine methyl ester (L-NAME; 2.2 microg, 22 microg, 220 microg and 2200 microg; an irreversible inhibitor of neuronal and endothelial NO synthase and reversible inhibitor of macrophage NO synthase) was administered via a bolus into the uterine artery. Nitrite/nitrate concentrations were: higher (P < 0.05) in the uterine vein as compared to the uterine artery on days 1-5 of the oestrous cycle; lower (P < 0.05) in the uterine artery as compared to the ovarian and uterine veins as well as in the ovarian artery as compared to the ovarian vein on days 8-13 of the cycle; lower (P < 0.05) in the uterine artery as compared to the ovarian artery and uterine and ovarian veins on days 17-20. Administration of NP at doses of 2.4 microg and 24 microg and L-NAME at all doses examined did not affect (P > 0.05) the blood pressure in the uterine artery in all periods examined. NP at a dose of 240 microg decreased (P < 0.001) the blood pressure in the arteries in all periods examined as compared to blood pressure before NP treatment. The results obtained indicate that NO is involved in the regulation of blood flow through the porcine reproductive tract. Moreover, our results suggest that the action of NP in the porcine uterine artery is not dependent on the phase of the oestrous cycle.

The influence of nitric oxide on the contractile activity of the isolated porcine ovarian and uterine arteries.

The aim of the present study was to investigate the influence of nitric oxide (NO) on the contractile activity of the isolated porcine ovarian and uterine arteries. Segments of the vessels, obtained from the pigs on days 1-5, 8-13 and 17-20 of the oestrous cycle, were mounted in the organ bath with Krebs-Ringer solution and contractile activity changes of the vessels were measured using isometric transducers. In Experiment I the arteries pretreated with norepinephrine (NE; 10(-7) M) were treated with sodium nitroprusside (SNP, 10(-8)-10(-4) M), a NO donor. In Experiment II administration of NE (10(-7) M) was preceded by treatment with Nomega-nitro-L-arginine methyl ester (L-NAME, 10(-8)-10(-6) M), an inhibitor of NO synthase. Donor of NO at doses of 10(-8)-10(-7) M did not affect (P>0.05) the contractility, while at doses of 10(-5)-10(-4) M caused a dose-dependent relaxation (P<0.05) of both ovarian and uterine arteries in all periods examined. Moreover, SNP at doses of 10(-6)-10(-4) M it caused significantly higher (P<0.05) relaxation of the ovarian arteries collected on days 8-13 as compared to the vessels from days 1-5 of the cycle. Pretreatment of the vessels with L-NAME caused a dose-dependent, significant (P<0.05) increase in the vasocontractile action of NE in both the ovarian and uterine arteries as compared to contractile activity of NE administered alone. Moreover, L-NAME pretreatment at a dose of 10(-6) M caused significantly higher (P<0.05) intensification of NE action in ovarian and uterine arteries collected on days 8-13 as compared to the vessels from days 1-5 (P<0.05) and 17-20 (P<0.05) of the oestrous cycle. Obtained results indicate that NO plays an important role in the regulation of the contractile activity of the isolated porcine ovarian and uterine arteries. Our data suggest that this action may be, at least in a part, dependent on the hormonal status of the organism.

Histochemical localization of NADPH-d-positive structures in bovine uterine and ovarian arteries during the oestrous cycle and early pregnancy.

The aim of the present study was to histochemically demonstrate nitric oxide synthase-related NADPH-d activity in ovarian and uterine arteries of heifers at different stages of the oestrous cycle and during early pregnancy. Catalytic activity of NADPH-d activity was found in the endothelial lining of all examined vessels, however, staining intensity was higher in the segments ipsilateral to the corpus luteum than in those taken from the contralateral side. Moreover, the reaction was much more intense during the luteal than during the follicular stage of the cycle. Similar differences were observed for NADPH-d activity in the muscular coat. In conclusion, the present results suggest that the endothelial/muscular cells may be the main source of nitric oxide in the studied parts of the bovine arteries, and also that NADPH-d activity may depend on the hormonal status of the organism.