High plasma levels of catecholamines during insulin-induced hypoglycemic stress do not cause beta-adrenergic receptor sequestration.
In the present investigation insulin-induced hypoglycemia was used as a powerful stimulus to rapidly release epinephrine from the adrenal medulla. Insulin injection raised epinephrine 16-fold and doubled norepinephrine plasma levels. The aim of this attempt was to induce beta-adrenergic receptors (beta-ARs) sequestration in vivo on mononuclear leukocytes (MNLs). The number of total and surface beta-ARs was significantly increased 30 minutes after insulin administration, with only partial recovery at 90 minutes. No detectable receptor sequestration was observed: surface receptors were about 90% of total receptors in all the conditions examined. Isoproterenol-stimulated cyclic adenosine monophosphate (cAMP) accumulation was also increased after 30 minutes (+66%) and 90 minutes (+65%) of insulin injection. Basal and forskolin-stimulated intracellular cAMP values were unchanged. We conclude that, even after a strong release of catecholamines, beta-AR redistribution cannot be demonstrated on MNLs.
Negri
F
F
Policlinico S. Matteo, Pavia, Italy.
Fratelli
M
M
Fratino
P
P
Melzi d'Eril
G
G
Finardi
G
G
De Blasi
A
A
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism; D000328:Adult; D002395:Catecholamines / Q000097:blood*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004837:Epinephrine / Q000097:blood; D005260:Female; D006801:Humans; D007003:Hypoglycemia / Q000097:blood* / Q000139:chemically induced* / Q000503:physiopathology; D007328:Insulin / Q000009:adverse effects* / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007962:Leukocytes / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D008875:Middle Aged; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D013312:Stress, Physiological / Q000139:chemically induced
D002395:Catecholamines; D007328:Insulin; D011943:Receptors, Adrenergic, beta; D005576:Colforsin; D000242:Cyclic AMP; D007545:Isoproterenol; D004837:Epinephrine