Submission Number: DAN-4-4-8

Abstract Number: 414

IMMUNOLOCALIZATION OF ENDOTHELIAL NITRIC OXIDE SYNTHASE (ENOS) IN OVINE CORPORA LUTEA (CL) THROUGHOUT THE ESTROUS CYCLE.

DR Arnold, V Doraiswamy, KC Kraft, DA Redmer and LP Reynolds

Dept Animal & Range Science, North Dakota State Univ, Fargo, North Dakota. ¹

Abstract:
Nitric oxide (NO), a potent vasodilator, has been shown to stimulate angiogenesis and expression of vascular endothelial growth factor (VEGF). This experiment was conducted to evaluate: 1) eNOS immunolocalization; and 2) colocalization of eNOS and VEGF in ovine CL throughout the estrous cycle. The CL were obtained from superovulated ewes slaughtered on day 2, 4, 10, and 15 (n=5/group) of the estrous cycle. For immunolocalization of eNOS in paraffinembedded luteal tissue sections (6 m), we used a specific antibody (Transduction Lab.) and the ABC method. Positive staining (% of tissue area stained) was quantified by image analysis. VEGF immunolocalization utilized a specific affinitypurified antibody (Redmer et al., J Reprod Fert 108:157165,1996). The endothelium of the luteal arterioles stained positive for eNOS regardless of day of estrous cycle, whereas thecalderived connective tissues tracts were devoid of staining. Capillary endothelium stained positive for eNOS in early cycle CL (days 2 and 4), but this staining was reduced dramatically later in the cycle (days 10 and 15). On day 2, eNOS staining was prominent (5.5%; pooled SEM= 0.8) in capillary and arteriolar endothelial cells within the parenchymal lobules; this immunostaining increased (P<0.01) on day 4 (8.2%), but decreased (P<0.01) on days 10 and 15 (2.4 and 1.3%, respectively). On days 10 and 15, eNOS immunostaining was localized primarily to endothelial cells of the arterioles. Luteal endothelial eNOS immunostaining was closely associated with periendothelial (capillary pericyte and arteriolar smooth muscle) VEGF immunostaining. We believe these results are the first to demonstrate eNOS localization in luteal capillary endothelial cells. In addition, these data provide evidence for a paracrine mechanism that maximizes luteal vasodilation and angiogensis via endothelial eNOS and periendothelial VEGF expression. Supported by NRICGP/USDA grant 98352036222.

Keywords: eNOS, Ovine, Corpus Luteum, Immunolocalization

This abstract is being presented at: 2:15 PM in session:
SESSION 14: CORPUS LUTEUM II