male genital system Male 92 rat 76 animal experiment 62 endocrine system 60 nonhuman 56 Rats 52 Animal 48 Support, Non-U.S. Gov't 44 epididymis 42 radioisotope 42 article 40 Testosterone 36 testosterone 32 Animalia 30 animal cell 30 priority journal 30 Animals 28 Castration 28 Epididymis 28 unclassified drug 28 Rats, Inbred Strains 24 androgen 22 castration 22 human 22 human cell 22 in vitro study 22 male 20 Female 18 Human 18