Stage dependent transfer of systemically injected foreign protein antigen and radiolabel into mouse ovarian follicles

The appearance of albumin‐like antigen and of radioisotope in mouse ovarian follicles following the systemic injection of 10 mg human serum albumin I131 (HSAI131) was studied by immunohistological and autoradiographic methods. Both isotope and antigen appeared in granulosa cell cytoplasm, ooplasm and oocyte nuclei in similar (or identical) positions. Qualitative impressions from fluorescent antibody preparations were that follicle stages (I, smallest; IX, largest) differed in relative amounts of detectable albumin‐like antigen. In addition, autoradiographic grain counts over 1421 follicles, compared by Sign Test, demonstrated statistically significant stage differences in amount of isotope detected. Radiolabel (and HSA‐like antigen) in ooplasm was highest at Stages I and VII‐IX and lowest at Stage III. Granulosa cell amounts were highest at Stage III and higher than or equal to ooplasm amounts at every other stage (except, perhaps IX). The relative amount of “label,” antigenic or isotopic, in oocyte nuclei was always less than in ooplasm and increase or decrease occurred one stage later than in ooplasm. The relative amount of radiolabel in ovarian blood vessels always exceeded that in granulosa cells and oocytes. The data are consistent with the interpretation that: (a) systemically injected foreign protein was transferred without major degradation from the blood to constituent cells of the mouse ovarian follicle; (b) transfer was stage dependent; (c) transfer occurred both before granulosa cells completely surrounded the oocyte and after oocyte microvilli and granulosa cell processes interdigitated; and, (d) transfer followed a concentration gradient.