Gene expression of type I phospholipase A₂ in pancreatic beta cells. Regulation of mRNA levels by starvation or glucose excess

Messenger RNA from intact rat pancreatic islets, or from transformed hamster beta (HIT) cells, hybridized with the cDNA probe for type I (but not type II) phospholipase A₂. The levels of phospholipase A₂ mRNA increased in islets from fasted rats: they decreased in islets cultured in a high glucose concentration (control values at 5.5 mM glucose = 150±6% of those at 22 mM) which impaired subsequent insulin secretion (reduction in second-phase release = 70±11%). These studies uniquely demonstrate that type I phospholipase A₂ is expressed specifically in beta cells and that nutrient availability modulates transcript levels, an effect which could contribute to the detrimental influence of prolonged hyperglycemia on islet function.