Abstract
Previous studies had pointed to 1) glucose-glucagon and 2) glucose-insulin feedback
mechanisms operating under physiological variations of plasma glucose concentration.
The present series of experiments was designed to see if insulin exerted a direct
effect on glucagon secretion.
Small doses of insulin, at 3 different concentrations, were infused or injected IV
into 47 fasted geese and peripheral blood samples taken shortly afterwards. Insulin
and GLI were measured using radioimmunological techniques. The non-specific glucagon
antibody used measured mainly pancreatic glucagon in the fasting Goose. While an infusion
of saline over one hour was ineffective, 2.5 mU/kg of insulin over 10 minutes provoked
a significant drop in GLI at the 6th minute. A drop in glycaemia was observed only
later and explained the return of the glucagonaemia to normal.
With 5 mU/kg/min over 10 minutes, this phenomenon was exaggerated. The inhibitory
effect was still evident at 10 minutes, despite a glycaemia significantly lower than
at zero time.
A rapid injection of 200 mU insulin gave similar results, but after 10 minutes the
resulting hypoglycemia restored the GLI above basal level and masked the inhibitory
effect of insulin.
It was concluded that insulin inhibits glucagon secretion in the Goose, this effect
being secondarily masked by the hypoglycemia.
Key words
Goose - Physiological Conditions - Inhibitory Effect - Insulin - Glucagon
