Animals controlled study nonhuman 2,681 article 2,188 priority journal 1,849 animal experiment 1,318 animal cell 1,222 Mice 996 mouse 981 animal tissue 974 animal 968 male 893 Male 883 female 874 Female 845 unclassified drug 745 metabolism 657 animal model 650 protein expression 648 Humans 621 Article 590 Rats 573 rat 557 human 551 physiology 404 enzyme activity 394 Animalia 366 human cell 327 in vitro study 322 signal transduction 305