Microcirculation of human pancreatic islets transplanted under the renal capsule of nude mice

Background. The aim was to measure the capillary blood pressure in transpla nted human islets. Methods. Human islets were isolated at the Central Unit of the beta -cell T ransplant in Brussels, Belgium. After transport to our laboratory, the isle ts were im. planted under the renal capsule of normoglycemic nude mice. Two weeks later the capillary and venous blood pressures in the islet graft an d adjacent renal parenchyma were measured with a micropuncture technique. Results. Capillary blood pressure was approximately 5-8 mmHg in both graft and renal capillaries: twice as high as in native islets. Venous blood pres sures were similar (4-5 mmHg) in the veins draining the graft and in the re nal interlobular veins. All veins leading from the graft emptied into the r enal parenchyma, that is, into interlobular veins. Conclusions. The capillary hypertension seen in transplanted human islets i s probably necessary to secure adequate drainage through the renal veins. W hether this contributes to the poor results of longterm islet graft surviva l is unknown.