Effect of residual endogenous insulin secretion on the abnormal oxytocin response to hypoglycaemia in insulin-dependent diabetics.
OBJECTIVE
Arginine-vasopressin (AVP) and oxytocin (OT) secretions are abnormally stimulated by hypoglycaemia in patients with IDDM. Since previous studies showed that AVP secretion is influenced by the persistence of residual endogenous insulin secretion, we wondered whether this factor also regulates OT secretion.


METHODS
Case-control study: the OT response to insulin-induced hypoglycaemia was measured in normal and diabetic patients with or without residual endogenous insulin secretion.


METHODS
Ten normal male subjects, 10 C-peptide positive (CpP) and 11 C-peptide negative (CpN) male diabetic patients.


METHODS



BACKGROUND
plasma C-peptide levels were measured after intravenous administration of 1 mg glucagon. Insulin tolerance test (ITT): diabetics were studied after optimization of their metabolic status by 3 days of treatment with constant subcutaneous insulin infusion. CpP and CpN diabetics and normal controls were tested with an intravenous administration of 0.15 IU per kg body weight insulin. Blood samples for OT assay were taken just before the rapid injection of insulin (time 0) and at time 15, 30, 45 and 60 min.


RESULTS
The basal concentrations of OT were similar in all groups. Insulin induced a similar hypoglycaemic nadir in all groups at 30 min, even though diabetic groups showed a delayed recovery in blood glucose levels. The glycaemic pattern was similar in all diabetic patients. Hypoglycaemia-induced OT rise was significantly higher in the two diabetic groups than in the normal group. However, CpN patients showed significantly higher OT increments than CpP subjects.


CONCLUSIONS
These data indicate that a residual endogenous insulin secretion exerts a partial protective action against the hypothalamic-pituitary disorder affecting the OT secretory system in IDDM.
Department of Internal Medicine, University of Parma, Italy.
R
R
Volpi
P
P
Chiodera
L
L
Capretti
G
G
Caffarri
N
N
Giuliani
A
A
Caiazza
V
V
Coiro
D000328:Adult; D001786:Blood Glucose; D002096:C-Peptide / Q000097:blood; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D005934:Glucagon / Q000494:pharmacology*; D006801:Humans; D007003:Hypoglycemia / Q000139:chemically induced / Q000378:metabolism*; D007275:Injections, Intravenous; D007328:Insulin / Q000008:administration & dosage / Q000009:adverse effects / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D010121:Oxytocin / Q000097:blood / Q000378:metabolism*
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D010121:Oxytocin; D005934:Glucagon