EFFECT OF HYDROCORTISONE AND EPINEPHRINE ON GLUCOSE UPTAKE BY THE RAT DIAPHRAGM1

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Abstract
Hydrocortisone inhibited glucose uptake by the rat diaphragm incubated in a Krebs-Ringer phosphate medium, when added in vitro at a concentration of 40 μg./ml., or when injected into rats at dose levels of .3 mg. daily for 7 days, or 2 mg. 6 hours before sacrifice. In a bicarbonate medium, 1 and 5 mg. doses of hydrocortisone were totally ineffective and a 10 mg. dose had only a slight effect on glucose uptake. The in vitro addition of 4 or 40 μg. of hydrocortisone to the bicarbonate medium, or of 40 μg. of hydrocortisone to the phosphate medium in which the concentration of Mg ions had been raised twofold, did not affect glucose uptake. Adrenalectomy increased basal glucose uptake by the diaphragm and abolished the inhibitory effect of epinephrine on glucose uptake. Hydrocortisone in vitro did not restore the epinephrine effect. The combined addition of epinephrine in vitro and of hydrocortisone either in vitro or in vivo to normal diaphragms incubated in the phosphate medium produced an inhibition of glucose uptake which was not greater than that produced by either of these hormones alone. The combined in vitro addition of cpinephrine and hydrocortisone to diaphragms incubated in the bicarbonate medium, had no effect on glucose uptake. It is suggested that an inhibition of the phosphofructokinase reaction by inorganic phosphate is responsible for the varying effects of hydrocortisone obtained in the different incubating media.

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