Animal Reproduction Science 138 (2013) 188–193 Contents lists available at SciVerse ScienceDirect Animal Reproduction Science journal h om epa ge: www.elsevier.com/locate/anireprosci Changes in blood flow in ovine follicles and serum concentration of estradiol 17 beta (E2) and nitric oxide (NO) around the time of ovulation in Ossimi ewes T.M. EL-Sherry a,∗ , R. Derar a , R. Bakry b a Department of Theriogenology, Faculty Vet Med, Assiut University, 71526, Egypt b Department of Oncological Clinical Pathology, South Egypt Cancer Institute, Assiut University, Egypt a r t i c l e i n f o Article history: Received 25 September 2011 Received in revised form 19 February 2013 Accepted 28 February 2013 Available online 20 March 2013 Keywords: Doppler E2 P4 Nitric oxide Follicles Ewes a b s t r a c t The aim of the present study was to examine the relation between follicular blood flow of the ovulatory follicle and the levels of serum E2 and nitric oxide (NO) in Ossimi ewe. Seven cyclic ewes were synchronized with a double injection PGF 2 . The follicular wave was examined daily until ovulation (disappearance of the large dominant follicle ultrasonographically) with transrectal color Doppler ultrasonography (8–10 MHz linear array transducer). The number of recruited follicles was 4.8 ± 0.9 (3–8 follicles) with diameter of 2.8 ± 0.1 mm. The interval from PGF2 injection to follicle deviation was 2.35 ± 0.07 days. The diameter of the first largest follicle (LF1) at recruitment day was 4 ± 0.3 mm while the diameter of the second largest follicle (LF2) was 3.7 ± 0.1 mm. The diameter of LF1 at the day of deviation was 5.1 ± 0.5 mm while the diameter of the LF2 was 4 ± 0.7 mm. The diameter of the ovulatory follicle was 6.1 ± 0.5 at day of ovulation. We detected the blood flow area of the ovulatory follicle at D2. At ovulation, the blood flow area and blood flow area percent increased significantly to be 11.9 ± 0.6 mm 2 and 44 ± 3.4% respectively. The results showed a positive correlation between E2 and NO (r = 0.85, P < 0.009). Both increased concomitantly with the diameter of the ovulatory follicle. Besides, NO and E2 reached a maximum level at ovulation (12.1 ± 1.8 ng/ml and 16.4 ± 1.7 pg/ml respectively). © 2013 Elsevier B.V. All rights reserved. 1. Introduction Color doppler ultrasonography is a useful, non-invasive technique for evaluating vascularity. It allows visual obser- vation of the blood flow in a limited area of the preovulatory follicular wall (Brannstrom et al., 1998; Acosta et al., 2003) and within CL (Miyazaki et al., 1998; Acosta et al., 2002). It has been used to assess cyclic changes of micro vessels in the ovine ovaries (Marret et al., 2006). Also, it was con- sidered as a better predictor of the outcome of in vitro fertilization and embryo transfer than the analysis of the ∗ Corresponding author. Tel.: +2 088 2334699; fax: +2 088 2 366503. E-mail address: timorsherry@yahoo.com (T.M. EL-Sherry). follicular fluid (Kim et al., 2004). The character of blood vas- cularity of individual follicles during growth (Acosta et al., 2005) and the local changes in blood flow within the pre- ovulatory follicle described in cattle (Acosta et al., 2003). In cattle, follicles >2.5 mm has been assessed for the presence or absence of blood flow of the dominant and subordi- nate follicles before and after selection (Acosta et al., 2004, 2005). It was found that follicles with detectable blood flow had a larger diameter than those with undetectable blood flow (Acosta et al., 2005). Moreover, local blood flow of ovu- latory follicle in the theca externa increased rapidly before ovulation (Acosta et al., 2003). Nitric oxide (NO) is a potent vasodilator which is involved in folliculogenesis and ovulation with other locally produced substances, growth factors and cytokines 0378-4320/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.anireprosci.2013.02.019