Markedly decreased oxygen tension in transplanted rat pancreatic islets irrespective of the implantation site

In this study, we syngeneically transplanted islets to three different implantation sites of diabetic and nondiabetic rats, then 9-12 weeks later we measured the blood perfusion and compared the tissue partial pressure of oxygen (Po-2) levels of these transplanted islets to endogenous islets. Modified Clark microelectrodes (outer tip diameter 2-6 mum) were used for the oxygen tension measurements, and islet transplant blood perfusion was recorded by laser-Doppler flowmetry (probe diameter 0.45 mm). The islet graft blood perfusion was similar in all islet grafts, irrespective of the implantation site. In comparison, the three implantation organs (the kidney cortex, liver, and spleen) differed markedly in their blood perfusion. There were no differences in islet graft blood perfusion between diabetic rand nondiabetic recipients. Within native pancreatic islets, the mean Po-2 was similar to 40 mmHg; however, all transplanted islets had a mean Po-2 of similar to5 mmHg. The oxygen tension of the grafts did not differ among the implantation sites. In diabetic recipients, an even lower Po-2 level was recorded in the islet transplants. We conclude that the choice of implantation site seems less important than intrinsic properties of the transplanted islets with regard to the degree of revascularization and concomitant blood perfusion. Furthermore, the mean Po-2 level in islets implanted to the kidney, liver, and spleen was markedly decreased at all three implantation sites when compared with native islets, especially in diabetic recipients. These results are suggestive of an insufficient oxygenization of revascularized transplanted islets, irrespective of the implantation site.