Gαolf identification by RT-PCR in purified normal pancreatic B cells and in islets from rat models of non-insulin-dependent diabetes

Recent reports using immunohistochemistry have shown that G alpha olf which shares 88% homology with G alpha s was expressed in pancreatic islets. To test the specificity of the expression of this G protein isotype in rat islet cells, B and non-B cells were separated by flow cytometry. The expression of G alpha olf and adenylyl cyclases (AC) of types II, III, V, and VI was evaluated by reverse-transcriptase polymerase chain reaction (RT-PCR). Since alterations in the expression of AC III were recently reported in the GK rat (a model of non-insulin-dependent diabetes mellitus, NIDDM), we also have analyzed the mRNA expression of G alpha olf and AC isoforms in pancreatic islets from GK rats and from adult rats neonatally treated by streptozotocin (nSTZ rats), another model of NIDDM. Southern blots of amplicons generated with specific primers of G alpha olf revealed the presence of a 540-bp band only in B cells. AC of types II, III, V, and VI were expressed both in B and non-B cells. However, AC III mRNA was clearly more abundant in non-B than in B cells. Moreover, in B cells the expression of AC VI was higher than that of AC V, whereas equal expressions of AC V and AC VI were found in non-B cells. In GK rat islets, the mRNA expressions of G alpha olf, AC TI, and AC III were clearly increased and no change in AC V and AC VI was found. In nSTZ rat islets, G alpha olf expression was barely detectable, but AC II and AC III mRNA levels were higher than those observed in controls. In conclusion, G alpha olf mRNA appeared specifically expressed in islet B cells and was increased in GK islets. The steady-state mRNA levels of AC II and AC III were clearly increased in the islets of the two rat models of NIDDM. Thus, alterations in the expression of G protein isotypes and AC isoforms could contribute to the diabetic phenotype. (C) 1999 Academic Press.