Glucose sensitivity of porcine and human islets in vitro

Preliminary experiments about the suitability of different commonly used cu lture media in our laboratory indicated, that prolonged exposure to high gl ucose concentrations during low temperature culture (LTC) impairs the viabi lity of long term cultured human islets. As a consequence of the heterogeni ty of tested media the present study was aimed to evaluate the influence of different glucose concentrations on survival, viability and in-vitro funct ion of cultured human islets in order to optimize islet survival until tran splantation and to compare species dependent differences in glucose sensiti vity. Quantified aliquots of freshly isolated (digestion-filtration, ficoll gradient purification) islets from consecutively processed human (n=6) and porcine (n=11) pancreata were subjected to different glucose concentration s (human islets: 500, 750, 1000 and 2000 mg/l; porcine islets: 1000 and 200 0 mg/l) in CMRL (22 degrees C) for X-IO days. After LTC survival, viability and glucose-stimulated insulin release of incubated tissue was assessed. A reduction of glucose concentration promotes survival and viability of huma n islets but impairs in vitro function at the same time, presumably due to a reduced glucose oxidation as expressed by the significantly reduced stimu lation index. In contrast to these findings in the human, elevated glucose concentration in porcine islet culture increases survival but reduces the g lucose-stimulated insulin release and the viability of cultured islets. The contradiction of the results in regard to islet survival related to islet viability are still unclear in the pig and needs further evaluation.