PARENT SESSION
SLIDE SESSION 19: ENDOCRINOLOGY OF PREGNANCY
Chairs: Mike Henson, Caniel Castracane, Deborah Edwards (Trainee)
Univ Ottawa-Monpetit 202
1:30 PM-3:30 PM
454
CIRCULATING LEVELS OF NITRIC OXIDE (NO) AND VEGF DURING OVINE PREGNANCY.
Magness, Ronald1,2, Vonnahme, Kimberly3, Li, Yun1, Rupnow, Heidi1, Phernetton, Terrance1, Ford, Stephen3, 1 2 3
ABSTRACT- Introduction: During the last third of pregnancy in the ewe, dramatic elevations in uterine blood flow (UBF), NO production and eNOS expression in uterine and placental artery endothelium coincide with maximal fetal growth and substantial cotyledonary neovascularization. VEGF has been reported to increase eNOS expression and NO production in endothelial cell cultures. We therefore hypothesized that circulating VEGF levels will be elevated in association with increased circulating NO levels during ovine gestation. Methods: Circulating NO measured as Nitrates/Nitrites (NOx) and VEGF concentrations were analyzed in systemic plasma obtained from 47 pregnant sheep ranging from 36 days of gestation until one week postpartum. Uterine venous-arterial NOx and VEGF concentrations were also analyzed from 5 additional chronically instrumented late gestation sheep. Results: Circulating levels of NOx were unaltered between 36 and 89 days of gestation averaging 4.7±0.44 uM (n=27), but rose progressively (P<0.01) to 10.3±1.3 uM (n=39) and 18.8±0.88 uM (n=149) at 90-109 and 110-145 days of gestation, respectively. During the postpartum period, NOx returned to initial basal levels (5.7±1.3 uM; n=16). Systemic NOx levels were approximately 30-40% higher in pregnancies with multiple fetuses (twin and triplets) versus singletons (P<0.05). Moreover, the rise in NOx levels were observed earlier in gestation in multiples (>90 days) as compared to singleton pregnancies (>110 days). In contrast to NOx, circulating levels of VEGF were not substantially altered from 36-145 days of gestation or into the postpartum period. Although multiples tended to have slightly greater VEGF levels then singletons (P<0.05), this was only observed from 75-110 days of gestation. No uterine venous-arterial concentration differences of either NOx or VEGF were observed. Conclusion. The pattern of the rise in NO in circulating plasma was not directly associated with changes in VEGF regardless of the number of fetuses present. Support: NIH HL49210, HL57653, HD33255, HL56702, and HD38843.
KEY WORDS: VEGF, Nitric Oxide, Pregnancy, Uterus