Effect of hCGbeta-tt immunization on ovarian morphology in hamster implanted with human choriocarcinoma.

Histological analysis of ovaries from hamsters immunized with hCGbeta-tt and implanted with human choriocarcinoma has shown that the gonadotropic activity of hCG was neutralized for 5 days of tumor growth. In control immunized hamsters, hCG secreted from the tumor induced the formation of large, cystic follicles, thecal luteinization and an increase in ovarian mass from Days 1-10 of tumor growth. In contrast, ovarian morphology in hCGbeta-tt immunized hamsters on Days 1-5 of tumor growth resembled that of non-tumor bearing hamsters. Normal follicular growth and corpora lutea formation were observed despite the secretion of hCG by the tumor. Gonadotropic stimulation, as indicated by the presence of cystic follicles, was not evident until Day 10 of tumor growth in hamsters immunized with hCGbeta-tt. hCGbeta-tt immunization did not affect ovarian structure or the normal estrus cycle in hamsters without tumors. These results indicate that the biological activity of hCG in vivo can be inhibited by active immunization with hCGbeta-tt.