Role of epinephrine during insulin-induced hypoglycemia in fasted rats.
Responses to insulin-induced hypoglycemia in fasted sham-operated (SHAM), adrenodemedullated (ADM), and epinephrine-infused ADM (ADM + E) rats were studied to ascertain the specific role of epinephrine in increasing resting skeletal muscle content of adenosine 3',5'-cyclic monophosphate (cAMP) and fructose 2,6-bisphosphate (F-2,6-P2), which are involved in stimulation of muscle glycogenolysis and lactate production. Rats from each group were fasted for 24 h and then infused intravenously with insulin (30, 60, or 90 min) to produce plasma insulin values of approximately 92 microU/ml. One-half of the insulin-infused ADM rats were also infused with epinephrine (ADM + E). Muscle and blood lactate, muscle cAMP, and muscle F-2,6-P2 increased and muscle glycogen decreased in SHAM rats. Each of these changes was prevented or attenuated in ADM rats and restored in ADM + E rats. Liver cAMP, glycogen, and F-2,6-P2 responses to hypoglycemia were similar in SHAM, ADM, and ADM + E rats. Blood glucose decreased to 0.74 +/- 0.05 mM in ADM rats compared with 1.54 +/- 0.11 mM in SHAM and 1.34 +/- 0.15 mM in ADM + E rats after 90 min of insulin infusion. The increase in plasma epinephrine is therefore essential in the counterregulatory response to insulin-induced hypoglycemia in fasted rats. Resting skeletal muscle glycogenolysis and lactate production for hepatic gluconeogenic substrate appear to be important components of the counterregulatory response in fasted rats.
Zoology Department, Brigham Young University, Provo, Utah 84602.
W W
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Winder
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MacLean
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Chandler
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W
Huang
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Mills
D000313:Adrenal Medulla / Q000502:physiology; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000502:physiology; D006152:Cyclic GMP / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D006003:Glycogen / Q000378:metabolism; D007003:Hypoglycemia / Q000139:chemically induced / Q000503:physiopathology*; D007328:Insulin / Q000494:pharmacology*; D007773:Lactates / Q000097:blood / Q000378:metabolism; D019344:Lactic Acid; D008099:Liver / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D001786:Blood Glucose; D007328:Insulin; D007773:Lactates; D019344:Lactic Acid; D006003:Glycogen; D006152:Cyclic GMP; D004837:Epinephrine