Effect of alpha-adrenergic blockade on pituitary hormonal responses to insulin-induced hypoglycemia in humans.
Arginine vasopressin, oxytocin and ACTH are released from the pituitary gland in response to acute hypoglycemia. To investigate the role of alpha-adrenergic mechanisms in mediating this response, 6 non-diabetic subjects were studied during hypoglycemia induced by 0.15 IU/kg i.v. insulin under control conditions, and during non-selective alpha-adrenergic blockade with phentolamine. In the control study plasma arginine vasopressin rose from 1.6 +/- 0.8 pmol/l (mean +/- SEM) basally to a maximum of 2.5 +/- 0.8 pmol/l following hypoglycemia (p less than 0.05). An exaggerated response was found during phentolamine blockade, with a maximum plasma vasopressin of 11.5 +/- 0.4 pmol/l (by analysis of variance, p less than 0.05). The plasma oxytocin response to hypoglycemia was similarly increased during phentolamine compared to control. Plasma growth hormone rose to 94 +/- 19 mU/l, and during blockade with phentolamine the response was significantly reduced reaching a peak of 34 +/- 7 mU/l (by analysis of variance, p less than 0.05). ACTH and prolactin both increased in response to hypoglycemia, but the increases were not affected by phentolamine. An alpha-adrenergic mechanism appears to inhibit the release of arginine vasopressin and oxytocin in response to hypoglycemia, but does not appear to affect the secretion of ACTH.
Diabetic Department, Royal Infirmary, Glasgow, UK.
B M
BM
Fisher
S
S
Thornton
D A
DA
Hepburn
J J
JJ
Morton
P H
PH
Baylis
G H
GH
Beastall
C E
CE
Gray
B M
BM
Frier
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000328:Adult; D001127:Arginine Vasopressin / Q000097:blood*; D006801:Humans; D007003:Hypoglycemia / Q000097:blood* / Q000139:chemically induced; D007328:Insulin; D008297:Male; D010121:Oxytocin / Q000097:blood*; D010646:Phentolamine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D007328:Insulin; D001127:Arginine Vasopressin; D010121:Oxytocin; D000324:Adrenocorticotropic Hormone; D010646:Phentolamine