THE INFLUENCE OF DEXAMETHASONE ON ADIPOSE TISSUE METABOLISM IN VITRO

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Abstract
SUMMARY: The influence of dexamethasone on the metabolism of incubated rat epididymal fat pads was investigated. In the presence of dexamethasone the glucose uptake and lactate and pyruvate outputs of the tissue, the concentration ratio lactate: pyruvate in the medium at the end of the incubation and the tissue content of glycogen, glucose-6-phosphate and l-glycerol-3-phosphate were decreased. No changes were observed in the rate of pyruvate utilization, the tissue content of ATP, ADP, AMP and citrate or the output of glycerol. Studies on the kinetics of glucose uptake indicated that in the presence of dexamethasone the maximal rate of uptake (Vmax) was decreased from 0·63 mg./g. wet tissue/hr. to 0·31 mg./g. wet tissue/hr., whereas the glucose concentration in the medium for half-maximal uptake (Ku) (0·29 mg./ml.) was not changed. These results confirmed that the effects of dexamethasone on the tissue were slow in onset, only appearing after 2 hr. pre-incubation with the hormone, but insulin (500 μ-u./ml.) released completely and rapidly the inhibition of glucose uptake induced by dexamethasone. Dexamethasone was also found to cause a small reduction in the incorporation of [1-14C]glycine into adipose tissue protein and nucleic acid fractions.