Superovulation with an anti-inhibin monoclonal antibody improves the reproductive performance of rat strains by increasing the pregnancy rate and the litter size

Abstract The rat is a multiparous rodent that has long been used in biomedical research, but the low reproductive performance in some rat strains hampers their broader use as research models. This study examined whether superovulation using an anti-inhibin monoclonal antibody (AIMA) could increase the litter size following natural mating in rats. In outbred Wistar rats, AIMA administration increased the number of ovulated oocytes by 1.3-fold. Importantly, AIMA did not affect fertilization and subsequent embryonic development, resulting in a 1.4-fold increase in litter size with a high pregnancy rate (89%). In contrast, conventional superovulation by equine/ human chorionic gonadotrophin administrations decreased the pregnancy rate to 6% and failed to increase the litter size. In inbred Brown Norway rats, AIMA increased the litter size 1.2-fold, and the pregnancy rate increased more than twice (86% vs. 38% in controls). AIMA also increased the litter size 2.0- and 1.5-fold in inbred Fischer 344 and Tokai High Avoider rats, respectively. Overall, when considering the pregnancy rate, AIMA increased the efficiency of offspring production 1.4-, 2.7-, 1.8-, and 1.5-fold in four rat strains. Thus, AIMA may consistently improve the reproductive performance by natural mating in rats, readily enabling their efficient use in biomedical research.