Successive Puncture of the Dominant Follicle followed by Ovulation and Fertilization: A New Experimental Model for the Study of Follicular Maturation in the Mare1 (original) (raw)

1995, Biology of Reproduction

The aims of this study were to determine whether successive follicular puncture in the mare may influence future follicular growth, oocyte maturation, and embryo viability; to examine the correlation between follicular maturation and concentrations of steroid hormones in the follicular fluid (FF); and to analyze proteins through use of two-dimensional (2D) PAGE. Ovaries often ponies (26 cycles) were examined. When the dominant follicle reached 25 mm, three successive punctures (PI, P2, P3) were performed every second day (Day 1 = day of PI, Day 3 = day of P2, Day 5 = day of P3) and 0.4-0.6 ml of FF was aspirated by means of a transvaginal ultrasonograph-guided technique. On the day after P2, mares were inseminated and embryos were collected 7 to 9 days after ovulation. Of a total of 26 PI follicles, 4 ovulated, 5 became atretic, and 17 survived. Six of these 17 ovulated after P2, and 11 survived. After P3, 5 of the 11 ovulated, 3 luteinized, and 3 regressed. In the 17 mares whose follicles had been subjected to two or three punctures, embryo collection was attempted from the 6 and 5 mares that ovulated after P2 and P3, respectively, yielding 4 and 2 embryos. The average diameter of follicles was from 27.2 ± 0.4 mm before PI to 27.8 ± 1.3 mm at P2 and 26.5 ± 1.8 mm at P3. The follicles in some groups increased in diameter (p < 0.05), some showed little change, and follicles in one regressing group showed a significant decrease to 20.3 ± 1.8 mm. The average concentration of estradiol was from 3989 ± 771 ng/ml to 742 ± 172 ng/ml (p < 0.05). The average concentration of A 4-androstenedione at PI was 42 ± 10 ng/ml; this value increased to 120 ± 28 ng/ml at P2 (p < 0.01) and at P3 decreased to 96 ± 36 ng/ml. The mean concentration of progesterone at PI was 79 ± 14 ng/ml; this value increased (p < 0.05) to 487 ± 227 at P2 and to 4507 ± 1162 at P3 (p < 0.001). All the proteins present in FF after silver staining were also present in the serum sample. We measured some of the differences between individual follicles during their growth towards ovulation. We found that after two or three punctures and collection of small volumes of FF every second day, some follicles still had good environmental conditions for maturation of oocytes that remained able to produce embryos.