GLUTATHIONE-MEDIATED PRESERVATION AND ENHANCEMENT OF ISOLATED PERIFUSED ISLET FUNCTION

It has been shown that myocardial tissue function may be better preser ved if antioxidants are incorporated into the reoxygenation medium at the end of the ischemic period following isolation of the organ. Altho ugh isolated pancreatic islets are prone to ischemic-reperfusion injur y, it is not clear if antioxidants have a role in the preservation of their function. The purpose of the present study, therefore, was to ex amine the effect of the addition of glutathione (GSH) to a physiologic incubation medium on pancreatic islet response to glucose stimulation . Islets isolated by microdissection were preperifused at the rate of 1 ml/min for 1 hr at 37 degrees C, with Krebs-Ringer bicarbonate (KRB) buffer containing 1% albumin, 5.5 mM(basal) glucose without (control) or with 10 mM glutamine or 10 mM GSH and maintained at pH 7.4 by cont inuous gassing with 95/5% O-2/CO2. After preperifusion, basal effluent samples were taken on ice for 20 min. The perifusion was then continu ed for 20 min with the KRB containing 27.7 mM glucose alone, followed by another 20 min of basal glucose washout. Solutions were changed usi ng a stopcock and all effluent perifusate samples obtained were stored frozen at -20 degrees C until radioimmunoassay for insulin. Total ins ulin output in the control group increased from a basal 11.45 +/- 3.18 to 29.23 +/- 7.08 ng/6 islets/20 min (P < 0.001, n = 5) when the gluc ose concentration was raised to 27.7 mM. During a 20-min washout, insu lin secretion was still significantly raised and did not return to the prestimulation basal rate. In the glutamine-treated islets, insulin o utput increased from 7.23 +/- 0.94 to 16.83 +/- 2.25 ng/6 islets/20 mi n (P < 0.001, n = 5) with 27.7 mM glucose stimulation and the signific antly raised washout basal rate of secretion did not return to the pre stimulation level. GSH treatment not only caused an enhanced 27.7 mM g lucose stimulation (8.46 +/- 1.99 to 38.72 +/- 11.51 ng/6 islets/20 mi n, P < 0.001, n = 6) of insulin output but also completely restored th e basal rate of insulin secretion to the prestimulation level within t he 20-min washout perifusion. In conclusion, these data show that incu bation of isolated islets with GSH enhanced their secretory response t o glucose stimulation and preserved their functional integrity. (C) 19 95 Academic Press, Inc.