Autonomic regulation of plasma insulin, glucagon and growth hormone responses to feeding in sheep fed a diet supplemented with calcium propionate

Abstract

The role of the autonomic nervous system in the regulation of plasma insulin, glucagon and growth hormone (GH) responses to supplemental propionate was investigated in rams. The rams were fed alfalfa hay cubes supplemented with 10 mmol kg−1 d−1 of calcium propionate. Saline, phentolamine, propranolol, atropine or hexamethonium were separately infused for 135 min starting 15 min before feeding. During saline infusion, the concentrations of plasma insulin and glucagon increased (P < 0.05) after the initiation of feeding, whereas plasma GH concentrations tended to decrease. Plasma insulin responses to feeding tended to be reduced by atropine and hexamethonium infusions. Plasma glucagon responses were abolished by atropine, hexamethonium and phentolamine infusions. It is suggested that in rams fed a propionate supplemented diet, the release of insulin and glucagon increases in response to feeding. Insulin release is mediated by activation of the parasympathetic nervous system, although responses were not significant in this study, while glucagon release is mediated both by activation of the parasympathetic nervous system and by the adrenergic α-receptors of the sympathetic nervous system. This study does not support a role for the autonomic nervous system in the regulation of GH release. Key words: Autonomic nervous system, insulin, glucagon, growth hormone, propionate, sheep