Glucoregulatory function of glucagon in hypo-, eu- and hyperthyroid miniature pigs.
The glucoregulatory function of glucagon was investigated in hypo-, eu- and hyperthyroid miniature pigs. Infusion glucagon, (3 ng x kg body weight-1.min-1) transiently increased blood glucose (p less than 0.01) and hepatic glucose production (p less than 0.01) in euthyroidism, but was without effect in hyperthyroidism. Infusing glucagon plus somatostatin (2 ng x kg body weight-1.min-1 and 0.2 microgram x kg body weight-1.min-1) transiently increased blood glucose (delta 3.0 to 4.3 mmol/l) and hepatic glucose production (delta 3.3 to 7.7 mumol x kg body weight-1.min-1) in all thyroid states, the effect was less pronounced in hyperthyroid pigs. By contrast, hypoglucagonaemia (74 to 107 pg/ml) at basal insulin (28 to 35 microU/ml) provoked hypoglycaemia (1.4 to 2.2 mmol/l) and a fall in glucose production (delta 4.7 to 8.3 mumol x kg body weight-1.min-1), which was independent of the thyroid state; the effect was most pronounced in hyperthyroidism (p less than 0.01). Hepatic glycogen content, arterial gluconeogenic precursor concentrations as well as the glycaemic response (delta 0.60 mmol/l) to alanine infusion (23 mumol x kg body weight-1.min-1) were all unaffected by hyperthyroidism. We conclude that moderate experimental hyperthyroidism reduces glucagon action due to reduced glycogen mobilisation. This may in part result from increased insulin sensitivity.
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D005934:Glucagon / Q000097:blood / Q000494:pharmacology*; D006980:Hyperthyroidism / Q000503:physiopathology*; D007037:Hypothyroidism / Q000503:physiopathology*; D007328:Insulin / Q000097:blood*; D008112:Liver Glycogen / Q000378:metabolism; D008297:Male; D009919:Orchiectomy; D012016:Reference Values; D013004:Somatostatin / Q000494:pharmacology; D013552:Swine; D013556:Swine, Miniature; D013961:Thyroid Gland / Q000502:physiology*
D001786:Blood Glucose; D007328:Insulin; D008112:Liver Glycogen; D013004:Somatostatin; D005934:Glucagon