IM: To study the synergistic effect of G (glucagon, 0 02
mg·kg -1 ), H (hydrocortisone, 20 mg·kg -1 ) and
E
(phenylephrine+isopro￣terenol, both 1 mg·kg -1 ) during insulin
induced hypoglycemia (IIH) in rats with 6 h of food deprivation (F 6
group). METHODS: I (insulin, 1 U·kg -1 ) was injected ip and 30
min later saline (F 6+I group), H, G and E individually or combined
(G+H, G+E, H+E and G+H+E) were all injected ip and all experiments
started 1 h after I injection. RESULTS: The rise in glycemia with
H+G+E was greater than the sum of the responses to ip H, G and E
individually or in double combination plus any single hormone. This
effect was reproduced by G+H+Iso (isoproterenol, 1 mg ·kg -1 ),
G+H+Iso+Met (metoprolol, 1 mg·kg -1 ) and G+H+Sal (salbutamol, 1
mg·kg -1 ). A clear relationship was shown between glycemia and
free fatty acids levels. Liver
gluconeogenesis from glycerol (2
mmol·L -1 ) was higher in the group which received G+H+β
adrenergic agonist vs control rats (F 6 or F 6+I groups).
CONCLU￣SION: (a) Acute hyperglycemia is obtained from a condition of
IIH by combined ip of G+H+β adrenergic agonists; (b) This effect
cannot be ascribed to a single hormone, but is a consequence of the
combined effects of these substances; (c) Blood insulin levels and
liver glycogen have no participation; (d) Lipolysis mediated by a β
adrenergic mechanism and gluconeogenesis from glycerol contribute to
the hyperglycemia.