CARBOHYDRATE METABOLISM IN THE ISOLATED DIAPHRAGM OF ADRENALECTOMIZED RATS AS AFFECTED BY EXPOSURE TO ADRENALINE IN VIVO AND IN VITRO

Abstract

Hemidiaphragms of adrenalectomized rats which had been nembutalized prior to decapitation, were incubated under aerobic conditions and the glucose uptake and glycogen deposition were measured. Addition of adrenaline in vitro induced marked glycogen degradation and a relative small decrease in glucose uptake. Pretreatment with adrenaline in vivo, however, appeared to increase glycogen deposition in vitro while glucose uptake increased to an equivalent extent. This effect was attributed to the low initial glycogen content induced by this treatment. Double exposure to adrenaline by administering this substance both in vivo and in vitro, neither affected glucose uptake nor glycogen deposition as compared with untreated control diaphragms. However, there was a significant difference in the glycogen level at which both groups metabolized, this level being extremely low in diaphragms doubly exposed to adrenaline. It was concluded that the action of adrenaline on muscular carbohydrate metabolism consists basically of three different stages: 1. A temporary initial stage during which glucose assimilation is inhibited secondarily to glycogen degradation. 2. A second stage, in which the occurrence of inhibition of glucose assimilation is determined by the fact whether in the corresponding control tissue the glucose uptake is raised in favour of glycogen deposition. 3. A stage of recovery induced by discontinuing the exposure to adrenaline. This stage is characterized by glycogen deposition and an equivalent rise in glucose assimilation.