Ancillary follicle and secondary corpora lutea formation following exogenous gonadotropin treatment in the domestic cat and effect of passive transfer of gonadotropin-neutralizing antisera

Abstract

A combination regimen of equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) was used to stimulate ovarian follicular development in domestic cats. The rate of elimination of eCG from circulation was estimated, and, following follicular aspiration, the formation of ancillary follicles and secondary CL was characterized. The effect of gonadotropin-neutralizing antisera on the development of secondary ovarian structures, CL function and humoral immune responses also was evaluated. After intramuscular injection, initial serum eCG concentrations were variable, with the elimination half-life estimated at 39 to 55 h and eCG persisting in circulation for several days. Following follicular aspiration, queens formed CL equal to the number of aspirated follicles and exhibited a rapid increase in progesterone concentration but developed high numbers of ancillary follicles by 5 d post aspiration. By 15 d post aspiration, all ancillary follicles had luteinized to form secondary CL. Treatment with neutralizing antisera at the time of follicular aspiration slowed (P < 0.05) CL formation but did not decrease (P > 0.05) the number of ancillary follicles or secondary CL. Progesterone concentrations did not differ (P > 0.05) from control queens while secondary humoral immune responses to eCG were qualitatively similar between groups. In summary, eCG was eliminated slowly from cats following intramuscular injection and this persistence in circulation may have contributed to the development of ancillary follicles and secondary CL. However, the administration of neutralizing antisera at the time of follicular aspiration was ineffective in preventing the formation of these secondary ovarian structures.