CAPILLARY BLOOD-PRESSURE IN SYNGENEIC RAT ISLETS TRANSPLANTED UNDER THE RENAL CAPSULE IS SIMILAR TO THAT OF THE IMPLANTATION ORGAN

The aim of the present study was to measure capillary blood pressure a nd interstitial pressure in transplanted pancreatic islets and to corr elate these measurements to capillary and tubular pressures in the adj acent kidney. For this purpose, 250 syngeneic islets were implanted un der the renal capsule of WF rats and studied 1, 2, or 6 months after t ransplantation. Some of the animals studied after 1 and 2 months mere streptozotocin (STZ) induced diabetic. Measurements were performed dur ing basal conditions or after an acute glucose-stimulation of insulin release. The hydrostatic pressures were determined in vivo by direct m icropuncture. The islet transplant capillary pressure in normoglycemic animals was 6.9 +/- 0.4 mmHg (n = 9), 10.0 +/- 0.8 mmHg (n = 7), and 12.4 +/- 0.8 mmHg (n = 7) when measured 1, 2, and 6 months after impla ntation, respectively. Previous data from our laboratory showed that t he normal capillary pressure of native rat pancreatic islets is simila r to 3 mmHg. The blood pressure in kidney peritubular capillaries was 10-12 mmHg in both transplanted and control animals. Islet transplant interstitial pressures were 4-6 mmHg in the normoglycemic recipients a t 1, 2, and 6 months after transplantation. Acute glucose stimulation had no effect on islet transplant interstitial pressure or peritubular or transplant capillary blood pressures. Capillary pressures in the i slet grafts were slightly increased 1 month after transplantation in S TZ-induced diabetic rats, and this was associated with an increased bl ood perfusion of the transplants. However, 2 months after transplantat ion there were no differences in transplant capillary blood pressure b etween diabetic and normoglycemic animals. The graft interstitial pres sure was, on the contrary, decreased in the diabetic animals 2 months after transplantation. We concluded that the capillary blood pressure in islets implanted under the renal capsule was similar to that of the implantation organ, which was three to four times higher than that no rmally found in native islets.