Background:
@EN Recently, there are several reports that diabetic hyperglycemia is not only the consequence of insulin deficiency but also affects the functions of pancreatic islets. The controversies of hyperglycemic effects on islet function are mainly due
to the
duration of exposure to hyperglycemia and other modifying factors such as interleukin-1 beta which may influence the islet functions.
In the present study, we observed the effect of hyperglycemia and combined effect of hyperglycemia and interleukin-1 beta on the insulin secretion of rat islets for short-term and long-term period by long-term culture system which we have
recently
established.
@ES Method:
@EN We obtained pancreatic islets of male Sprague-Dawley rats, weigning 80~100g, isolated by collagenase method and Ficoll density gradient centrifugation method. To observe the effect of a few days exposure to hyperglycemia, islets were cultured
for 2
or 3 days in culture medium RPMI 1640 containing 11. 1 or 27.7mM/L glucose. Thereafter islets were cultured for 6 days with daily change of culture media with 1.1 mM/L glucose.
To investigate the relationship between dose of IL-1βand various glucose concentrations, islets were cultured in medium RPMI 1640 containing various concentrations of glucose(2., 8, 5, 5, 11 1 and 22.2mM/L), with or without IL-1β(0.5 pM, 2nM)
for
14
days. We measured total accumulated insulin secretion every day by RIA method.
@ES Result:
@EN 1) Threshold level of glucose stimulated insulin secretion of islets is above 5.5mM.
2) A period of three days exposure to high glucose concentration did not seem to impair the function of islets in terms of insulin secretion.
3) Glucose and IL-1β stimulated the insulin secretin of islets as dose dependent manner for the first 2 hours. But, insulin secretion was markeldy suppressed by high dose of IL-1β at 24 hours.
4) In a low dose of Il-1β, glucose was dominant stimulator on the insulin secretion of islets and that in high dose of IL-1β, marked inhibitory action of the insulin secretion of islets was evident regardless of glucose concentrations during
long-term culture.
@ES Conclusion:
@EN Glucose concentration is thought to be an important determinant of interleukin-1 beta effect on insulin secretion and bimodal effect of interleukin-1 beta on the glucose stimulated insulin secretion of islets was evident. The effect of
interleukin-1
beta on the insulin secretion of islets depend on its concentration, duration of exposure and concentration of glucose, Further studies are needed to understand underlying mechanisms of these effects of interleukin-1 beta and glucose on the
islets
in
vitro.
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