title: Alpha-adrenoceptor involvement in catecholamine-induced hyperglycaemia in conscious fasted rabbits.
abstract: In conscious fasted rabbits an intravenous infusion of phenylephrine (20 micrograms kg-1 min-1) induced hyperglycaemia. The increase in blood glucose was accompanied by a modest increase in insulin secretion and a reduction of liver glycogen. Muscle glycogen and blood lactate levels were not altered by treatment with phenylephrine. Prazosin, 1 mg kg-1 s.c., partially attenuated phenylephrine-induced hyperglycaemia. Phenoxybenzamine infusion (16.6 micrograms kg-1 min-1) for 15 min suppressed the increase in blood glucose and the reduction in liver glycogen evoked by phenylephrine. This alpha-adrenoceptor blocker also clearly attenuated the blood glucose elevation observed on infusing adrenaline at 0.3 microgram kg-1 min-1. Blockade by phenoxybenzamine of phenylephrine- and adrenaline-induced hyperglycaemia was not accompanied by a significant increase in immunoreactive insulin plasma levels. Yohimbine infused at a rate of 20 micrograms kg-1 min-1, also completely blocked phenylephrine-induced hyperglycaemia. This suppressor effect was accompanied by a marked rebound in insulin secretion. It is concluded that in normal fasted rabbits stimulation of alpha-adrenoceptors induces hyperglycaemia. The increase in blood glucose depends mainly on liver glycogenolysis and inhibition of insulin secretion. Separate blockade of each component suffices to reduce alpha-adrenoceptor-mediated hyperglycaemia.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002395:Catecholamines / Q000494:pharmacology*; D005215:Fasting; D006003:Glycogen / Q000096:biosynthesis / Q000378:metabolism; D006943:Hyperglycemia / Q000139:chemically induced* / Q000503:physiopathology; D007328:Insulin / Q000097:blood; D007773:Lactates / Q000097:blood; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013997:Time Factors
chemical_list: D000317:Adrenergic alpha-Antagonists; D001786:Blood Glucose; D002395:Catecholamines; D007328:Insulin; D007773:Lactates; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D006003:Glycogen; D011224:Prazosin