The effect of an intravenous infusion of IGF-I and insulin on IGFBP-1, IGFBP-3, acid labile subunit, free and bound IGF-I, catecholamines and potassium in normal volunteers during an amino acid and glucose clamp.
OBJECTIVE
To investigate the effects of IGF-I and insulin at doses equipotent with respect to hypoglycaemic effect on IGF-I concentrations (free and bound), IGF binding proteins, catecholamines and potassium levels.


METHODS
A glucose and amino acid clamp technique was used to investigate the effects of a 3 h intravenous infusion of either IGF-I 43.7 pmol/kg/min (20 micrograms/kg/h) or insulin 3.4 pmol/kg/min (0.5 mU/kg/min).


METHODS
Circulating levels of total IGF-I, free and bound IGF-I, Insulin, IGFBP-1, IGFBP-3, ALS, catecholamines and potassium were measured.


METHODS
6 normal human volunteers aged 21-49.


RESULTS
During the IGF-I infusion, IGF-I levels increased (P < 0.01) (26.6 +/- 2.8-88.9 +/- 14.2 nmol/l) and insulin levels fell (P < 0.05) (16.7 +/- 2.9-7.2 +/- 1.6 mu/l). During the insulin infusion, insulin levels increased (P < 0.01) (11.7 +/- 1.6-56.7 +/- 16 mu/l) and there was no change in IGF-I. There was no significant change in IGFBP-3 or ALS during the IGF-I or insulin infusions. There was a significant (P < 0.05) fall in IGFBP-1 levels from 27.1 +/- 4.1-8.06 +/- 1.6 micrograms/l during the insulin infusion and a significant (P < 0.05) rise during the first 120 min of IGF-I infusion from 28.6 +/- 6.3-67.9 +/- 10.6 micrograms/l. There was a significant (P < 0.05) increase in free IGF-I and IGF-I bound to the 150 and 50 kD plasma fractions during the IGF-I infusion. At basal and the end of the IGF-I infusion adrenaline levels (pmol/l) were: 173 +/- 22 and 174 +/- 28; dopamine levels (pmol/l) were: 415 +/- 87 and 470 +/- 87; plasma potassium (mmol/l) was 4.2 +/- 0.06 and 3.56 +/- 0.13. At basal and the end of the insulin infusion adrenaline levels (pmol/l) were: 160 +/- 38 and 163 +/- 21; dopamine levels (pmol/l) were: 238 +/- 26 and 316 +/- 31; plasma potassium (mmol/l) was 4.2 +/- 0.07 and 3.92 +/- 0.17. There were no significant changes in plasma catecholamine concentrations with either infusion but potassium concentrations were significantly (P < 0.05) reduced during the IGF-I infusion.


CONCLUSIONS
We conclude that an infusion of IGF-I resulted in increased levels of both free and bound IGF-I. IGF-I and insulin under conditions of adequate substrate supply have acute effects on IGFBP-1 and potassium physiology, but have little effect on IGFBP-3, ALS or catecholamines.
Russell-Jones
D L
DL
Department of Medicine, UMDS, London, UK.
Umpleby
A M
AM
Shojaee-Moradie
F
F
Boroujerdi
M A
MA
Jones
R H
RH
Baxter
R C
RC
Sönksen
P H
PH
D000328:Adult; D000596:Amino Acids / Q000378:metabolism*; D002352:Carrier Proteins / Q000097:blood; D002395:Catecholamines / Q000097:blood*; D004298:Dopamine / Q000097:blood; D004837:Epinephrine / Q000097:blood; D015309:Glucose Clamp Technique; D006023:Glycoproteins / Q000097:blood; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000032:analysis / Q000494:pharmacology*; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood*
D000596:Amino Acids; D002352:Carrier Proteins; D002395:Catecholamines; D006023:Glycoproteins; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; C075944:insulin-like growth factor binding protein, acid labile subunit; D007334:Insulin-Like Growth Factor I; D011188:Potassium; D004298:Dopamine; D004837:Epinephrine