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.
Winder
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WW
Zoology Department, Brigham Young University, Provo, Utah 84602.
MacLean
P S
PS
Chandler
S L
SL
Huang
W
W
Mills
R H
RH
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