Increased density of glucagon receptors in liver from endurance-trained rats.
The binding properties of glucagon receptors were determined in plasma membranes isolated from liver of untrained (n = 6) and swimming endurance-trained Sprague-Dawley male rats (n = 7; 3 h/day, 5 days/wk, for 8 wk). Plasma membranes were purified from liver by aqueous two-phase affinity partitioning, and saturation kinetics were obtained by incubation of plasma membranes (10 microg of proteins/150 microl) with (125)I-labeled glucagon at concentrations ranging from 0.15 to 3.0 nM for 30 min at 30 degrees C. Saturating curve analysis indicated no difference in the affinity of glucagon receptors (0.57 +/- 0.06 and 0.77 +/- 0.09 nM in untrained and trained groups, respectively) but a significant higher glucagon receptor density in liver from untrained vs. trained rats (3.09 +/- 0.12 vs. 4.28 +/- 0.19 pmol/mg proteins). These results suggest that the reported increase in liver glucagon sensitivity in endurance-trained subjects (Drouin R, Lavoie C, Bourque J, Ducros F, Poisson D, and Chiasson J-L. Am J Physiol Endocrinol Metab 274: E23-E28, 1998) could be partly due to an increased glucagon receptor density in response to training.
Légaré
A
A
Département de chimie-biologie, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec G9A 5H7, Canada.
Drouin
R
R
Milot
M
M
Massicotte
D
D
Péronnet
F
F
Massicotte
G
G
Lavoie
C
C
D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000032:analysis; D005934:Glucagon / Q000097:blood; D007328:Insulin / Q000097:blood; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018027:Receptors, Glucagon / Q000378:metabolism*; D013550:Swimming / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
D007328:Insulin; D007457:Iodine Radioisotopes; D018027:Receptors, Glucagon; D005934:Glucagon; D002950:Citrate (si)-Synthase