Background/aims: Pancreatic acini of streptozotocin (STZ)-induced diabetic rats release amylase less than normal acini on cholecystokinin (CCK) stimulation. Pancreatic enzyme secretion has been closely related to the intracellular calcium concentration ([Ca2(+)](i)) of the acinar cell. In the present study, sequential changes of the intracellular calcium signal which probably underlie the altered enzyme secretion in response to CCK-8 were investigated using pancreatic acini from diabetic rats.
Methods: Diabetic rats were prepared by single intravenous injection of STZ (70 mg/kg). Stimulating experiments with CCK-8 were performed 7 days later. Pancreatic acini were isolated by collagenase digestion. Amylase release and [Ca2(+)](i) were measured by colorimethod and calcium imaging, respectively. The geometry of intracellular calcium signal was analyzed.
Results: Normal acini exhibited concentration-dependent [Ca2(+)](i) increase and regular oscillatory calcium signal on CCK-8 stimulation. Amylase release was also concentration-dependent. However, diabetic acini showed significantly less [Ca2(+)](i) increase, prolonged time to peak [Ca2(+)](i), decreased calcium spikes number, and decreased amylase release compared with normal acini. The decreased [Ca2(+)](i) in diabetic acini was restored significantly by insulin treatment.
Conclusions: Relatively decreased amylase release in diabetic pancreatic acini in response to CCK, appears to be associated with altered calcium signal due to insulin deficiency.
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