The character of endogenous retrovirus in pancreatic beta-cells of NOD mice.

The character of retrovirus type C in NOD mouse pancreatic-beta-cells was investigated. First, the in vitro response of retrovirus type C to glucose stimulation was examined. When the pancreatic islets of control NON mice were observed with an electron microscopy retrovirus types C could not be detected in the beta-cells with or without glucose stimulation. Retrovirus type C particles and intracisternal type A particles (IAPs) in NOD mouse pancreatic beta-cells increased by glucose stimulation, but the increase in retrovirus type C differed from that of IAPs. The clusters of retrovirus type C were found in some beta-cells, whereas IAPs were scattered in beta-cells. Next, we investigated the expression of retrovirus type C transcript in NOD mouse pancreatic islets. From polymerase chain reaction analysis using two primers of retrovirus type C designed from a conserved U3 region, a major product was found to be endogenous polytropic retrovirus (Pmv). The subcloned PCR probe and oligonucleotide probes specific for Pmv and modified polytropic retrovirus were used for Northern blot analysis. Pancreatic islets from NOD and NON mice (control mice) contained 8.4-kb and 3.0-kb Pmv transcripts. The quantity of transcripts of Pmv in NOD mouse pancreatic beta-cells were the same as that in NON mice. The transcript level of islets was much higher than those of thymus and liver. The appearance of retrovirus type C particles in beta-cells of NOD mice may involve the mechanisms by which diabetes is generated in NOD mice.