Effect of glucagon on hepatic lactate metabolism in the conscious dog.
The present experiments were undertaken to assess hepatic lactate metabolism in the overnight-fasted, conscious dog after a physiological elevation in glucagon. Animals were given somatostatin plus intraportal insulin (243 microU . kg-1 . min-1) and glucagon (0.65 ng . kg-1 . min-1) to initially fix the pancreatic hormone levels at basal values. After a 40-min control period the glucagon level was increased to 527 +/- 27 pg/ml, while the insulin level was left unchanged (10 microU/ml). Fifteen minutes later blood lactate had increased by 215 +/- 24 mumol/l because of a marked increase in lactate output by the liver [2.4 +/- 2.0 to 10.0 +/- 3.8 mumol . kg . min (P less than 0.05)]. Subsequently, hepatic lactate output decreased, and after 3 h the liver was taking up lactate at a rate of 3.1 +/- 1.6 mumol . kg-1 . min-1 (P less than 0.05). Gut and renal lactate production were not significantly affected by glucagon. The rate of conversion of lactate and alanine to glucose had tripled after 3 h of hyperglucagonemia, while the efficiency with which the liver converted the incoming gluconeogenic precursors to glucose had doubled. The fractional extraction of alanine by the liver had more than doubled by 3 h, and net hepatic alanine uptake had increased by 50%.(ABSTRACT TRUNCATED AT 250 WORDS)
Davis
M A
MA
Williams
P E
PE
Cherrington
A D
AD
D000409:Alanine / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D003243:Consciousness; D004285:Dogs; D005260:Female; D005934:Glucagon / Q000494:pharmacology*; D005943:Gluconeogenesis / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D007668:Kidney / Q000378:metabolism; D007773:Lactates / Q000378:metabolism*; D019344:Lactic Acid; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D013004:Somatostatin / Q000494:pharmacology
D007328:Insulin; D007773:Lactates; D019344:Lactic Acid; D013004:Somatostatin; D005934:Glucagon; D005947:Glucose; D000409:Alanine