Circulating sex steroids after induction of luteinized unruptured follicles in adult guinea pigs.

Luteinized unruptured follicles (LUFs) typically occur when exogenous gonadotropins are administered to adult female guinea pigs prior to the onset of ovulation. In this study, LUFs were induced with human chorionic gonadotropin (hCG) and serum steroids were measured for the next eight days. Serum progesterone was elevated following the hCG injection, but values did not reach the peak levels observed during untreated estrous cycles and declined prematurely. Serum estradiol was similar during untreated cycles and after hCG-treatment. Androstenedione and testosterone were elevated two days after the hCG injection but returned to baseline thereafter. The presence of LUFs was verified by ovarian histology of similarly treated animals. These results demonstrate that hCG-induced LUFs in adult guinea pigs are functionally deficient as compared to corpora lutea arising from spontaneous ovulation.