Medroxyprogesterone Acetate: MATERIALS AND METHODS(2)
The remaining seven ewes served as untreated controls. Daily transrectal ultrasonography of ovaries (performed between 1300 and 1500 h) started at —Day 5 after ovulation. The size and position of CL and ovarian antral follicles >3 mm in size were then recorded for 19 days. Ovarian ultrasonography was performed using a real-time, B-mode echo camera (Aloka SSD-500; Overseas Monitors Ltd., Richmond, BC, Canada) equipped with a stiffened, 7.5-MHz transducer. That this technique can accurately quantify ovarian antral follicles >3 mm in diameter and to detect CL have been shown previously. Ultrasonographic detection of ovulations has also been recently verified in our laboratory (unpublished) via laparotomy performed 1, 2, and 3 days after ovulation had been determined with transrectal ultrasonography. Twenty-three of 24 ovulations (96%) identified with ultrasonography were confirmed by laparotomy, and the single questionable ovulation was that of a 4-mm follicle.
In the present study, blood samples (10 ml) were collected each day before ultrasonographic examination by jugular venipuncture using vacu-tainers (Becton Dickinson, Rutherford, NJ). Three days after PGF2„ injection and MAP sponge insertion to treated ewes, all ewes were bled every 12 min for 6 h via indwelling jugular catheters (4 ml/sample; vinyl tubing, 1.00 mm inside diameter X 1.50 mm outside diameter; SV70, Critchley Electrical Products Pty Ltd., Auburn, NSW, Australia).