Abstract: 305

EXPRESSION OF NITRIC OXIDE SYNTHASE AND NITRIC OXIDE PRODUCTION IN THE OVINE PLACENTA DURING LATE PREGNANCY.

Jing Zheng^{1 *}, Yun Li¹ , Andrew Weiss¹ , Ian Bird¹ , Ronald Magness^{1 2 *}
Dept. of Ob/Gyn, Univ. of WI-Madison, WI ¹
Dept. of Animal Science, Univ. of WI-Madison, WI ²

To evaluate the expression of nitric oxide (NO) synthase (NOS), NO production, and the role of angiotensin II (ANG II) in NO production, placentas were obtained from ewes on Days 110, 120, 130, and 142 of pregnancy, and were separated into cotyledonary (COT), intercotyledonary (ICOT), caruncular (CAR), and intercaruncular (ICAR) components. Using immunohistochemistry, endothelial NOS (eNOS) was detected in all four placental components, primarily in endothelium, trophoblast cells, chronic epithelium, and luminal and glandular epithelium. For inducible NOS (iNOS), the positive staining was observed in ICOT and ICAR, primarily in stromal cells of subepithelium and luminal and glandular epithelium. Placental explants were cultured for 24 h in the absence or presence of ANG II (1M or 100M). NO (nitrite and nitrate) and bFGF levels in placental explant-conditioned media were determined by chemiluminesence and EIA. In COT, NO levels increased (P < 0.05) 1.5 fold from Day 110 to 130 and then declined (P < 0.05) at term. This change in COT was correlated (r² = 0.57, P < 0.05) with bFGF levels. In ICOT, NO levels increased 2.2 fold (r² = 0.96, P < 0.01) from Day 110 to Days 130 and 142. In CAR, NO levels were higher (P < 0.05) on Day 130 than those on Days 120 and 142. No change in NO levels was observed in ICAR. ANG II treatment at 100uM decreased NO levels in COT (P < 0.05) and CAR on Day 130. Thus, during late ovine pregnancy: 1) eNOS and iNOS are expressed in the placentas; 2) increased NO production by COT is associated with increases in bFGF production, suggesting that NO may partially modulate placental angiogenesis; 2) decreased NO production by COT and CAR at term may attenuate myometrium quiescence to prepare for parturition; and 3) ANG II may contribute in part to this decreases in NO production. Support: NIH HL57653 and AHA/WI Fellowship Award.

    This abstract is being presented on Monday, August 2 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.