Summary
Adrenergic effects on plasma levels of glucagon, insulin, glucose and free fatty acids
were studied in fasted rabbits by infusing epinephrine, norepinephrine, isoproterenol,
phentolamine (an adrenergic alpha-receptor blocking drug) and propranolol (an adrenergic
beta-receptor blocking drug).
The adrenergic effects on the plasma levels of insulin, glucose and free fatty acids
were similar to those found in other species. The plasma levels of insulin were increased
by beta-receptor stimulation (isoproterenol, phentolamine + epinephrine) and decreased
by alpha-receptor stimulation (epinephrine, norepinephrine, propranolol + epinephrine).
The plasma levels of glucose were increased by both alpha- and beta-receptor stimulation,
and the epinephrine-induced hyperglycaemia was only blocked by combined infusions
with phentolamine and propranolol. The plasma levels of free fatty acids were increased
by saline and further increased by beta-receptor stimulation (isoproterenol), while
epinephrine and nor-epinephrine gave variable results. Alpha-receptor stimulation
(propranolol + epinephrine) slightly decreased the plasma levels of free fatty acids.
The plasma levels of glucagon, however, were mainly increased by alpha-receptor stimulation
(epinephrine, norepinephrine, propranolol + epinephrine) and increased only to a minor
extent by beta-receptor stimulation (isoproterenol, phentolamine + epinephrine) in
rabbits. This is in contrast to results reported for humans, where beta-receptor stimulation
seems to be most important in stimulating glucagon release.
Key-Words:
Epinephrine
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Norepinephrine
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Isoproterenol
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Phentolamine
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Propranolol
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Glucagon
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Insulin
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Blood Glucose
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Free Fatty Acids
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Rabbits
