title: Glucose effectiveness is the major determinant of intravenous glucose tolerance in the rat.
abstract: To determine the importance of insulin for glucose disposal during an intravenous glucose tolerance test in rats, experiments were performed in four cohorts of conscious unrestrained rats fasted overnight. In cohorts 1-3, a bolus of tracer ([3-3H]glucose, 50 microCi) was given alone, with glucose (0.3 g/kg) to induce an endogenous insulin response (approximately 1,100 pmol/l), or with exogenous insulin to give physiological (1,700 pmol/l) or supraphysiological (12,000 pmol/l) plasma levels. Raising plasma insulin within the physiological range had no effect (P > 0.05), but supraphysiological levels induced hypoglycemia (7.3 +/- 0.2 to 3.6 +/- 0.2 mmol/l) and increased [3H]glucose disappearance rate (P < 0.001). In cohort 4, a primed, continuous tracer infusion was started 120 min before saline or glucose bolus injection. [3H]glucose levels fell 15-20%, and the disappearance rate rose 36% (P < 0.05) after glucose injection. These results indicate that in fasted rats a tracer bolus injection protocol is not sufficiently sensitive to measure the physiological effect of insulin released in response to a bolus of glucose because this effect of insulin is small. Glucose itself is the predominant mediator of glucose disposal after a bolus of glucose in the fasted rat.
authors: Diabetes Research Laboratory, School of Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6. finegood@sfu.ca
authors: M D
authors: MD
authors: McArthur
authors: D
authors: D
authors: You
authors: K
authors: K
authors: Klapstein
authors: D T
authors: DT
authors: Finegood
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism*; D005951:Glucose Tolerance Test; D007262:Infusions, Intravenous; D007275:Injections, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*; D000078790:Insulin Secretion; D007700:Kinetics; D008297:Male; D011865:Radioisotope Dilution Technique; D051381:Rats; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005947:Glucose