Involvement of the catecholaminergic system in glucagon-induced thermogenesis in Muscovy ducklings ( Cairina moschata )

Abstract

Physiological studies have shown that glucagon is a potential mediator of nonshivering thermogenesis (NST) in birds. The present work was undertaken in order to investigate whether the observed thermogenesis results from a direct action of glucagon on avian thermoregulatory mechanisms or in fact requires the participation of other agents such as catecholamines. Our experiments were performed using cold-acclimated (CA) ducklings which developed muscle NST. A comparison was made with thermoneutral (TN) ducklings of the same age. Our principal results showed that: (1) at ambient temperature (25 degrees C), circulating norepinephrine (NE) was markedly decreased in CA ducklings (-42%), while circulating epinephrine (E) did not undergo any consistent change; (2) in CA and TN ducklings, an intraperitoneal injection of glucagon (360 microg x kg(-1)) was followed after 10 min by prominent lipolysis and a large increase in circulating NE (4- to 6-fold) and E (14- to 17-fold), which was sustained for at least 1 h. The elevation of circulating NE was less pronounced in CA ducklings. The thermogenic action of glucagon in birds is probably indirect and involves at least the mobilization of lipids and sympatho-adrenal stimulation. The changes in peripheral noradrenergic activity during cold acclimation could be associated with adaptive changes leading to NST.

Mitochondrial oxidative energy metabolism in guanethidine-induced sympathectomized ducklings

“…Similarly, chronic guanethidine treatment leads to a fifty percent drop in norepinephrine concentrations in the heart and skeletal muscles of ducklings (Filali-Zegzouti et al 2000). Although the molecular and cellular mechanisms for this drop in plasma and tissues levels remain unclear, our data confirm that the oral administration of guanethidine in ducklings results in an effective sympathectomy (Filali-Zegzouti et al 2000).…”

“…In rats, Villanueva et al (2003) have shown that chemical sympathectomy with guanethidine selectively blocks the release of norepinephrine from the postganglionic nerve terminals, leading to a decrease in norepinephrine concentrations in several tissues, including skeletal muscles (Navegantes et al 1999;Villanueva et al 2003). Similarly, chronic guanethidine treatment leads to a fifty percent drop in norepinephrine concentrations in the heart and skeletal muscles of ducklings (Filali-Zegzouti et al 2000). Although the molecular and cellular mechanisms for this drop in plasma and tissues levels remain unclear, our data confirm that the oral administration of guanethidine in ducklings results in an effective sympathectomy (Filali-Zegzouti et al 2000).…”

Thermogenic Mechanisms and Their Hormonal Regulation

“…Despite the earlier belief that glucagon increased oxygen consumption in muscle (73), this has not been directly demonstrated (154). Both glucagon and epinephrine increase liver oxygen consumption, but this seems to be a reflection of the stimulation of gluconeogenesis in this organ (13,87). Both epinephrine and glucagon can also stimulate BAT, but it is not likely that such an effect is of major importance in temperature and energy homeostasis.…”

The influence of glucagon on the concentration of triacylglycerols and cholesterol in the liver and kidney of mice

“…by increasing the level of energy substrates in blood and using them at a higher rate. The energy management of the body is regulated by, among other things, glucagon (Filali-Zegzouti et al 2000, 2005, Robson-Doucette et al 2011. The mechanism of glucagon influencing fatty tissue adipocytes is known and it is closely associated with the system of receptor -adenyl cyclase -cAMP (Authier & Desbuquois 2008, Shyangdan et al 2011.…”