Hepatic nerves are not essential to the increase in hepatic glucose production during muscular work.
To establish the role of hepatic nerves in hepatic glycogenolytic and gluconeogenic regulation during exercise, dogs underwent a laparotomy during which the hepatic nerves were either left intact (C; n = 8) or cut (DN; n = 5). At least 17 days after surgery, dogs were studied during 150 min of treadmill exercise (12% grade, 100 m/min). Glucose production (Ra) and gluconeogenesis (GNG) were assessed by combining [3-3H]glucose, [U-14C]alanine, and indocyanine green infusions with arterial, portal vein, and hepatic vein sampling. Glucagon and insulin were similar at rest and exercise in both groups. Norepinephrine rose from 145 +/- 10 to 242 +/- 32 pg/ml by 150 min of exercise in C and from 150 +/- 25 to 333 +/- 83 pg/ml in DN. Epinephrine rose from 66 +/- 7 pg/ml at rest to 108 +/- 10 and 148 +/- 24 pg/ml after 30 and 150 min of exercise in C and from 90 +/- 15 pg/ml at rest to 185 +/- 33 (P less than 0.05 compared with C) and 194 +/- 36 pg/ml after 30 and 150 min of exercise in DN. Plasma glucose fell gradually from 108 +/- 2 and 106 +/- 3 mg/dl at rest to 96 +/- 4 and 92 +/- 8 by the end of exercise in C and DN, respectively. Ra was similar in C and DN rising from 3.2 +/- 0.2 to 8.7 +/- 0.6 and 2.6 +/- 0.2 to 7.5 +/- 1.1 mg.kg-1.min-1, respectively, by the end of exercise. Minimum and maximum rates of GNG from alanine, glycerol, and lactate were elevated in DN compared with C during rest and exercise. However, the exercise-induced changes in GNG were similar in both groups. In conclusion, nerves to the liver are not essential to the increased Ra and glucose homeostasis during moderate-intensity exercise.
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
D H
DH
Wasserman
P E
PE
Williams
D B
DB
Lacy
D
D
Bracy
A D
AD
Cherrington
D000409:Alanine / Q000378:metabolism; D000818:Animals; D003714:Denervation; D004285:Dogs; D004837:Epinephrine / Q000097:blood; D005934:Glucagon / Q000097:blood; D005943:Gluconeogenesis; D005990:Glycerol / Q000378:metabolism; D007328:Insulin / Q000097:blood; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D008099:Liver / Q000294:innervation / Q000378:metabolism*; D008102:Liver Circulation; D008112:Liver Glycogen / Q000378:metabolism*; D009132:Muscles / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D005082:Physical Exertion; D012016:Reference Values
D007328:Insulin; D007773:Lactates; D008112:Liver Glycogen; D005934:Glucagon; D000409:Alanine; D005990:Glycerol; D009638:Norepinephrine; D004837:Epinephrine