A method for a selective local application of radioactive precursors of nucleic acids to the cow ovary.

Abstract

Local application of /5-3H/uridine or /6-3H/thymidine to the cow ovary was obtained by the instillation of the radioactive solution into a rubber balloon ('bursa') tightly enclosing the organ exposed by laparotomy. After 30-90 min the exteriorized ovary was replaced in the abdominal cavity. Ovaries were recovered 1-8 days later and processed for autoradiography. After /5-3H/uridine application the peripheral layer of the ovary, containing the follicles in different stages of development was most intensely labelled. The labelling by /5-3H/uridine could be attributed prevailingly to the cytoplasm of different cells constituting the ovary but in some cases the labelling was higher in nuclei. The highest level of labelling was seen in the cytoplasm of follicular cells of follicles composed of one or two layers of cuboidal cells. Labelling was also detected in the ooplasm of oocytes with the maximal number of grains being seen in the first phase of their growth. On the other hand, no labelling was detected in the ooplasm of oocytes isolated from antral follicles the growth of which had been induced previously by hormonal treatment. It is believed that the labelling obtained by the described procedure represents to a significant degree RNA. A similar local application of /6-3H/thymidine allowed us to obtain labelling restricted specifically to nuclei of different cells composing the ovarian tissue. In the presented results, the entry of flattened follicular cells of primordial follicles in vivo in the S-phase of the cell cycle was demonstrated as well as an evident different proliferation rate in the successive stages of follicle development. The method proposed here may probably be the way for testing the effects of different substances, available only in small quantities, on the cow ovary.