Delayed and atypical D-glyceraldehyde-induced insulin secretion from the perfused duodenum pancreas of chicken

Insulin release by the isolated-perfused pancreas of 5-8 week-old chickens was studied in response to graded concentrations of D-glyceraldehyde (D-GA) (5-20 mM). D-GA was perfused for 30 min in the absence or in the presence of glucose concentrations (2.8 or 14 mM) which do not evoke insulin release alone. D-GA alone or in combination with glucose does not cause a biphasic insulin release. As compared to rodents the release is reduced and delayed (at least 16 min) and requires higher D-GA concentrations which reveals the insensitivity of the chicken pancreas to D-GA. In the absence of glucose, the release is higher at 15 mM D-GA. Glucose (2.8 or 14 mM) sensitized the pancreas to D-GA by eliciting earlier and higher insulin response but never restored an immediate and biphasic secretory response to D-GA. Glucose amplified the response to low D-GA levels (5 and 10 mM) and inhibited the response to higher concentrations (15 and 20 mM). A transient insulin rise ("off-response") related to the D-GA concentration was observed after withdrawal of D-GA either in the absence or in the presence of glucose. Therefore, in addition to glucose, the chicken pancreas is relatively insensitive to D-GA suggesting that the mechanism leading to insulin release in response to nutrient metabolism is different in chickens as compared to that in mammals.