The effect of FSH, LH, oestradiol-17 beta, and progesterone on cytoplasmic maturation of bovine follicular oocytes in vitro.

Bovine oocytes removed from follicles 2-5 mm in diameter were cultured for 24 h in the medium without hormone (control) and in the medium supplemented with 1 microgram FSH/ml, 1 microgram LH/ml, 250 ng oestradiol-17 beta/ml and 250 ng progesterone/ml. At the end of culture the zonae pellucidae were dissolved by pronase and the eggs were transferred to droplets of preincubated bovine epididymal spermatozoa. After incubation for 14-16 h, the number of penetrated oocytes, the average number of spermatozoa per one oocyte, and the stage of sperm nucleus chromatin decondensation were recorded. The highest number of penetrated oocytes (99.2%) was found in cultures with progesterone, but 83.7% oocytes were polyspermic and in 77.0% oocytes a normal male and a female pronucleus was formed, it was the highest incidence among all hormones tested. Oocytes cultured with oestradiol-17 beta were penetrated in 76.5% of cases, but in this group the largest number of monospermic oocytes with a female and a male pronucleus was seen. Also, the lowest number of spermatozoa per polyspermic oocyte was recorded. In cultures with FSH and LH, the percentage of fertilization was almost equal (62.2 and 61.1%, respectively). With FSH the lowest number of polyspermic oocytes was observed. From the results it follows that progesterone has a positive effect on the synthesis of MPGF in the cytoplasm of oocytes and on the number of penetrated oocytes. Oestradiol-17 beta and FSH probably participate in the formation of a polyspermic block via cortical granules.