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

Abstract

. 1999. Autonomic regulation of plasma insulin, glucagon and growth hormone responses to feeding in sheep fed a diet supplemented with calcium propionate. Can. J. Anim. Sci. 79: [449][450][451][452][453][454][455][456]. 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 Sano, H., Mori, Y., Takahashi, H. et Terashima, Y. 1999. Régulation autonome des réponses de l'insuline, du glucagon et de l'hormone de croissance dans le plasma chez des moutons recevant une alimentation complémentée avec du propionate de calcium. Can. J. Anim. Sci. 79: 449-456. Nous avons étudié chez des béliers le rôle du système nerveux autonome dans la régu-lation des réponses de l'insuline, du glucagon et de l'hormone de croissance (GH) dans le plasma sanguin à la présence d'un supplément de propionate dans l'aliment. Les béliers recevaient du foin de luzerne en cubes, enrichi de 10 mmol de propionate de calcium par kg d'aliment, par jour. Un soluté salin (témoin), de la phentolamine, du propranolol, de l'atropine ou de l'hexaméthonium étaient infusés séparément dans la jugulaire pendant 135 min à partir de 15 min avant le repas. L'infusion salée donnait lieu à un accroissement (P < 0,05) des concentrations plasmatiques d'insuline et de glucagon des le début du repas, tandis que les concentrations de GH suivaient une tendance à la baisse. Les réponses de l'insuline plasmatique à l'ingestion d'aliments parraissaient atténuées par les infusions d'atropine et d'hexaméthonium. Ces deux bloquants et la phentolamine effaçaient toute réponse du glucagon. Les résultats donnent à penser que chez les béliers recevant l'aliment complémenté au propionate les décharges d'insuline et de glucagon augmentent sous l'effet de l'alimentatio...

Effect of supplemental calcium propionate on insulin action to blood glucose metabolism in adult sheep

“…to be within the physiological range as described previously [24]. Sano et al [25] determined the postprandial changes in VFA concentrations in both the rumen fluid and blood in sheep supplemented with the same dose of propionate as in the present experiment.…”

“…Van der Walt [2] reported that in sheep fed lucerne hay at 12-h intervals, 15 to 22% of glucose turnover derived from propionic acid even at the prefeeding period. Plasma glucagon concentrations increased more after the initiation of feeding for the diet supplemented with calcium propionate than for the diet without supplementation [24]. Brockman and Bergman [31] and Brockman and Greer [32] reported that in sheep, glucagon infusion increased hepatic gluconeogenesis from alanine and glutamine but not from propionate.…”