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Aldosterone as well as its antagonist spirolactone prolong the survival time of allogeneic skin grafts from 10 to 14 days. The effect of a xenogeneic rabbit-anti-rat-lymphocyte serum is intensified by aldosterone; rats treated with ALS + aldosterone retained the allogeneic graft 5 days longer than those treated with ALS only. After large amounts of prednisolone the graft prolongation exceeded that of the aldosterone or spirolactone treated animals; the same is true for the combination with ALS. Prednisolone in a dose equivalent to the glucocorticoidal amount of the chosen aldosterone dose has no significant graft prolonging effect compared with the controls. Thus the graft-maintaining effect of aldosterone is believed to be independent of the glucocorticoidal component of this corticosteroid. The stimulation of endogenous aldosterone production is supposed to be responsible for the graft-prolonging effect of the aldosterone antagonist spirolactone. Clinical trials with aldosterone and spirolactone appear permissible in immunosuppressive therapy.

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Background: In the present study, a technique for computer-assisted, normothermic, oxygenated, ex vivo, recirculating small bowel perfusion was established as a tool to investigate organ pretreatment protocols and ischemia/reperfusion phenomena. A prerequisite for the desired setup was an organ chamber for ex vivo perfusion and the use of syngeneic whole blood as perfusate. Methods: The entire small bowel was harvested from Lewis rats and perfused in an organ chamber ex vivo for at least 2 h. The temperature was kept at 37°C in a water bath. Three experimental groups were explored, characterized by different perfusion solutions. The basic perfusate consisted of syngeneic whole blood diluted with either NaCl, Krebs’ solution or Krebs’ solution and norepinephrine to a hematocrit of 30%. In addition, in each group l-glutamine was administered intraluminally. The desired perfusion pressure was 100 mm Hg which was kept constant with a computer-assisted data acquisition software, which measured on-line pressure, oxygenation, flow, temperature and pH and adjusted the pressure by changing the flow via a peristaltic pump. The viability of the preparation was tested by measuring oxygen consumption and maltose absorption, which requires intact enzymes of the mucosal brush border to break down maltose into glucose. Results: Organ perfusion in group 1 (dilution with NaCl) revealed problems such as hypersecretion into the bowel lumen, low vascular resistance and no maltose uptake. In contrast a viable organ could be demonstrated using Krebs’ solution as dilution solution. The addition of norepinephrine led to an improved perfusion over the entire perfusion period. Maltose absorption was comparable to tests conducted with native small bowel. Oxygen consumption was stable during the 2-hour perfusion period. Conclusions: The ex vivo perfusion system established enables small bowel perfusion for at least 2 h. The viability of the graft could be demonstrated. The perfusion time achieved is sufficient to study leukocyte/lymphocyte interaction with the endothelium of the graft vessels. In addition, a viable small bowel, after 2 h of ex vivo perfusion, facilitates testing of pretreatment protocols for the reduction of the immunogenicity of small bowel allografts.