The role of the sympathetic system in the control of insulin release in response to hyperglycaemia in conscious calves.

Abstract

SUMMARY1. The effects of the adrenoceptor blocking agents, phentolamine and propranolol, on the release of pancreatic glucagon and insulin in response to exogenous glucose have been investigated in conscious 2-6-week-old calves.2. There were no significant differences between the changes in mean plasma glucagon or insulin concentration, which occurred in response to hyperglycaemia, in calves pre-treated with both propranolol and phentolamine, phentolamine alone and normal calves.3. However, the rise in mean plasma insulin concentration was effectively abolished by pre-treatment with propranolol alone and there was a small but significant fall in mean plasma glucagon concentration which was not observed in any of the other groups.4. The results are discussed in relation to previous studies of the role of the autonomic innervation to the endocrine pancreas in the control of insulin release during hyperglycaemia in conscious calves and weaned lambs.

The characteristics of β-adrenergic binding sites on pancreatic islets of Langerhans

“…Thus, the use of agonists selective for the ß-adreno¬ ceptor in combination with antagonists selective for the a-adrenoceptor can raise plasma insulin concen¬ trations. In contrast, ß-adrenergic antagonists suppress circulating plasma insulin levels (Lundquist & Ericson, 1978;Ahren & Lundquist, 1984;Bloom & Edwards, 1985). This latter effect is thought to be through inter¬ action with ß-adrenergic receptors on the cell sur¬ face of the islets of Langerhans.…”