Properties such as toxicity of substances may be determined by assaying properties, fates and effects of substances in an ex vivo metabolically active human organ or tissue under normothermic perfusion with a fluid containing a test substance. The data can be used as, for example, part of a submission to a government regulatory organization. Preferred methods use perfused endocrine gland organs or tissues to evaluate hormone or other bodily chemical disruption caused by substances and pre-donation diseased or injured organs or tissues.