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.
Fisher
B M
BM
Diabetic Department, Royal Infirmary, Glasgow, UK.
Thornton
S
S
Hepburn
D A
DA
Morton
J J
JJ
Baylis
P H
PH
Beastall
G H
GH
Gray
C E
CE
Frier
B M
BM
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