Clinical islet transplantation requires graft preservation conditions with a minimal loss in viable beta cells. The present study examines whether rat pancreatic beta cells survive a 96 h storage period at 4 degrees C. In a single cell viability assay, less than 20% viable cells were counted after 48 h storage in physiological HAM's F10 medium; cell survival was better in the high potassium solutions UW or Collins and further improved by supplementing Collins with albumin and benzamidine (CAB-77% viability after 96 h). Suspended beta cell aggregates were also well preserved during 4 days in CAB-4 degrees C as judged from DNA recovery and electron microscopy. After cold-storage in CAB, beta cells exhibited a higher insulin content than after culture in HAM's F10 at 20 degrees or 37 degrees C, but their capacity for subsequent insulin synthesis and release was comparable. When isolated islets were stored in CAB-4 degrees C for 96 h, they yielded slightly higher numbers of dissociated cells than after culture in HAM's F10 at 20 degrees C. Implantation of cold stored islets from 2 donor pancreata corrected hyperglycemia in streptozotocin-diabetic rats. It is concluded that rat beta cells can be stored in a supplemented Collins solution for at least 4 days at 4 degrees C, with preservation of initial cell number, hormone content and glucose responsiveness. During short-term periods, this new storage condition is at least equivalent to cultures at 20 degrees or 37 degrees C. Further studies are needed to assess any advantage for long-term storage of islet cell grafts.