Animals controlled study nonhuman article 2,100 priority journal 1,795 animal experiment 1,316 animal cell 1,220 animal tissue 974 mouse 965 Mice 961 animal 918 male 877 Male 861 female 858 Female 823 unclassified drug 714 animal model 648 metabolism 625 protein expression 621 Article 576 Rats 563 Humans 562 rat 551 human 474 physiology 391 enzyme activity 370 Animalia 364 in vitro study 306 Rats, Sprague-Dawley 293 signal transduction 287