Male Fischer 344 rats weighing 80-90 g were fed on a copper-depleted diet supplemented with 0.6% triethylenetetramine tetrahydrochloride (a copper chelator), and the death of pancreatic acinar cells of these rats was investigated morphologically and biochemically. The weight of the pancreas of these rats decreased from 3 weeks after feeding, and concomitantly the percentage of dead acinar cells increased to the maximum in about the 5th week and decreased subsequently. These dead acinar cells showed light microscopic and electron microscopic characteristics of apoptosis. Furthermore, the electrophoretic pattern of DNAs extracted from the pancreas having many dead acinar cells showed a ladder-like distribution, characteristic of apoptosis. The present results indicate that feeding of rats on a copper-depleted diet supplemented with a copper chelator results in apoptosis of acinar cells of the pancreas.