Increased role of skeletal muscle in the calorigenic response to glucagon of cold-acclimated ducklings.
The site of the calorigenesis observed in birds after glucagon was sought in control and cold-acclimated (CA) ducklings. Twenty-four 6-wk-old muscovy ducklings were reared either at thermoneutrality (TN) (25 degrees C) or in the cold (4 degrees C) from the age of 1 wk. Glucagon-induced calorigenesis (GIC) was estimated at 25 degrees C after a peritoneal glucagon injection (103 nmol/kg). Glucagon induced a higher increase in animal heat production (indirect calorimetry) and body temperature in CA (+45% and +1.1 degrees C) than in control ducklings (+30% and +0.4 degree C). In CA ducklings, the perfusion rate (thermal clearance method) and temperature of gastrocnemius increased (+130% and +1.0 degree C) shortly after glucagon, whereas tissue oxygenation (polarography) decreased (-34%). There was no significant effect of glucagon in TN controls. These changes, which peaked 45-60 min after glucagon injection, indicated a prolonged increase of muscle O2 consumption in CA ducklings. Leg muscle blood flow (radioactive microspheres) measured 45 min after glucagon was slightly increased in controls (+20%; P < 0.05), while in CA ducklings, the increase was larger (+76%; P < 0.05). The arteriovenous difference in O2 content was not markedly affected by glucagon in both groups. These parameters indicated an increase in leg muscle O2 uptake in response to glucagon of +29% in controls and +76% in CA ducklings. In controls, 28% of the GIC measured in vivo could be attributed to whole body skeletal muscles, compared with 53% in CA ducklings. The remaining part might be accounted for mostly by the liver.(ABSTRACT TRUNCATED AT 250 WORDS)
Duchamp
C
C
Laboratoire de Thermorégulation et Energétique de l'Exercice, Centre National de la Recherche Scientifique, Faculté de Médecine, France.
Chatonnet
J
J
Dittmar
A
A
Barré
H
H
D000064:Acclimatization; D000273:Adipose Tissue / Q000098:blood supply / Q000502:physiology; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects*; D002151:Calorimetry; D003080:Cold Temperature; D004372:Ducks / Q000502:physiology*; D004734:Energy Metabolism / Q000187:drug effects; D005934:Glucagon / Q000494:pharmacology*; D008099:Liver / Q000098:blood supply / Q000502:physiology; D008297:Male; D009132:Muscles / Q000098:blood supply / Q000378:metabolism / Q000502:physiology*; D009928:Organ Specificity; D010101:Oxygen Consumption; D012039:Regional Blood Flow; D013997:Time Factors
D005934:Glucagon