Gluconeogenesis and ketogenesis of in situ rat perfused liver submitted to short-term insulin-induced hypoglycaemia (IIH) were investigated. For this purpose, 24-h fasted rats that received intraperitoneal (ip) regular insulin (1.0 U kg(-1)) or saline were compared. The studies were performed 30 min after insulin (IIH group) or saline (COG group) injection. For gluconeogenesis studies, livers from the IIH and COG groups were perfused with increasing concentrations (from basal blood concentrations until saturating concentration) of glycerol, L-lactate (Lac) or pyruvate (Pyr). Livers of the IIH group showed maintained efficiency to produce glucose from glycerol and higher efficiency to produce glucose from Lac and Pyr. In agreement with these results the oral administration of glycerol (100 mg kg(-1)), Lac (100 mg kg(-1)), Pyr (100 mg kg(-1)) or glycerol (100 mg kg(-1)) + Lac (100 mg kg(-1)) + Pyr (100 mg kg(-1)) promoted glycaemia recovery. It can be inferred that the increased portal availability of Lac, Pyr and glycerol could help glycaemia recovery by a mechanism mediated, partly at least, by a maintained (glycerol) or increased (Lac and Pyr) hepatic efficiency to produce glucose. Moreover, in spite of the fact that insulin inhibits ketogenesis, the capacity of the liver to produce ketone bodies from octanoate during IIH was maintained.
Copyright 2007 John Wiley & Sons, Ltd.