Dynamics of Insulin and Glucagon Release in Rats: Influence of Dietary Manganese

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Abstract
The effect of Mn on endocrine pancreatic function was examined in Mn-sufficient (control) and Mn deficient (Mn-) Sprague-Dawley rats. Pancreatic insulin release was lower (P < 0.05) in Mn- rats than in controls in response to both a 300 mg/dl and a 100 mg/dl glucose stimulus. The 300 mg/dl glocose stimulus induced the synthesis of 19.4 .mu.g insulin/g pancreas in control rats. Additionally, no appreciable intracellular degradation of insulin occured over an 80-min perfusion period. In Mn-rats, there occurred an intracellular insulin degradation amounting to 7.8 .mu.g/g pancreas. This enhanced degradation was partially compensated by a net insulin synthesis of only 3.4 .mu.g insulin/g pancreas. Initial (min 1-3) insulin release by Mn-rats in response to 10 mM arginine was lower (P < 0.05) than that observed in controls. Pancreatic glucagon release in response to 10 mM arginine was not affected by Mn deficiency. Apparently, Mn deficiency results in depressed pancreatic insulin synthesis and enhanced degradation. These factors may be responsible for the abnormal carbohydrate metabolism observed in Mn-animals.

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