Abstract
Abstract
The relationship between β-endorphin(β-EP)/β-lipotropin(β-LP) and insulin secretion in the basal state and after glucose challenge was studied in obese male Zucker rats and their lean littermates. Baseline plasma β-EP/β-LP concentrations were similar in the two groups of animals. Baseline plasma insulin and serum glucose concentrations were significantly higher in the obese animals. Following glucose challenge, the increase in plasma β-EP/β-LP concentrations was significantly lower in the obese animals than in their lean littermates. Opioid blockade with naloxone failed to alter the baseline hyperinsulinemia and hyperglycemia seen in the obese animals. The data suggest that the hyperinsulinemia in the obese Zucker rat is not due to endogenous hyperendorp hinemia as shown in humans with polycystic ovary syndrome. The obese rats showed dissociation between glucose-stimulated plasma levels of β-EP/β-LP and insulin levels which may contribute to the hyperinsulinemia and insulin restance in these animals.
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