We found
that late passages of HIT cells serially cultured in media containing
11.1 mM glucose lost insulin responsivity and had
greatly diminished levels of insulin content and insulin mRNA.
In marked contrast, late passages of HIT cells cultured serially
in media containing 0.8 mM glucose retained insulin mRNA,
insulin content, and insulin responsivity to glucose in static incubations
and during perifusion with glucose. No insulin gene
mutation or alteration of levels of GLUT-2 were found in late
passages of HIT cells cultured with media containing 11.1 mM
glucose. These data uniquely indicate that loss of beta cell function
in HIT cells passed serially under high glucose conditions
is caused by loss of insulin mRNA, insulin content, and insulin
secretion and is preventable by culturing HIT cells under low
glucose conditions. This strongly suggests potential genetic
mechanisms of action for glucose tokicity of beta cells. (J. Clin.
Invest. 1992.90:320-325.) Key words: glucose toxicity * insulin
gene * diabetes mellitus