Animals controlled study nonhuman 2,818 article 2,332 priority journal 1,950 animal experiment 1,370 animal cell 1,300 Mice 1,068 mouse 1,048 animal tissue 1,010 animal 1,008 male 934 Male 926 female 906 Female 878 unclassified drug 790 protein expression 692 metabolism 688 animal model 678 Humans 660 Rats 602 Article 590 rat 582 human 578 physiology 424 enzyme activity 408 Animalia 388 human cell 346 in vitro study 336 signal transduction 330