Cryopreservation of isolated rat islets of Langerhans in the presence of ethylene glycol or dimethyl sulfoxide: evaluation of toxicity and the dynamic pattern of subsequent insulin release in vitro.

The toxic effect of ethylene glycol (EG) on the pattern of dynamic insulin release from rat pancreatic islets with or without freezing was investigated in comparison with that of dimethyl sulfoxide (Me2SO). Sixty islets were perifused (1 ml/min) consecutively with D-glucose (1.67 mM for 30 min followed by 16.7 mM for 60 min and 1.67 mM for 60 min) after exposure to 2.0 M EG or Me2SO for 1 h at either 22 or 0 degrees C. During the second period of perifusion, the insulin output from islets exposed to Me2SO or EG at 22 degrees C decreased to 53 and 51% of that from nontreated control islets, respectively. On the other hand, the islets exposed to EG at 0 degrees C exhibited 86% of the control insulin output under the same perifusion conditions, and this appeared to be higher than that of islets exposed to Me2SO (60%) at 0 degrees C. Frozen islets, after exposure to 2.0 M EG or Me2SO for 1 h at 0 degrees C, responded positively to 16.7 mM D-glucose, and the typical biphasic pattern of insulin secretion was observed. The insulin output from these islets during the second period of perifusion was not comparable to that from unfrozen control islets. In particular, the mean insulin output of EG-cryopreserved islets during the second period accounted for 99% of that from unfrozen control islets. The present findings suggest the possible use of EG as an alternative cryoprotectant to Me2SO.