A method of determining effects of at least one test substance or bioactive agent ex vivo, comprising: perfusing at least one ex vivo organ that has been determined to be unsuitable for transplantation with a first medical fluid such as herein described to preserve the at least one organ exposing the at least one organ to the at least one test substance or bioactive agent and gathering data regarding at least one of the at least one organ, the at least one test substance or bioactive agent, and interaction between the at least one organ and the at least one test substance or bioactive agent. The method includes perfusing the organ at hypothermic and/or normothermic temperatures, preferably after hypothermic organ flushing for organ transport and/or storage. The method can be practiced with prior or subsequent static or perfusion hypothermic exposure of the organ. Organ viability is restored by restoring high energy nucleotide (e.g., ATP) levels by perfusing the organ with a medical fluid, such as an oxygenated cross-linked hemoglobin-based bicarbonate medical fluid, at normothermic temperatures. During the period in which the organ is preserved and/or maintained, various drug research and development may be performed on and/or with the organ. The organ may be perfused with a fluid containing a substance such as a test substance or bioactive agent to obtain data regarding the organ, the substance and an interaction of the substance and the organ.
