The effect of adrenaline on the uptake of glucose, mannose and fructose in the rat diaphragm.

Abstract

Summary.1. The effect of adrenaline on the uptake of hexose in the isolated diaphragm, and the mechanism of the inhibition of the uptake of glucose by adrenaline have been investigated in the present work.2. The uptake of hexose in the isolated diaphragm exhibits the following sequence glucose >mannose > fructose. Adrenaline inhibits the uptake of mannose to the same degree as glucose. With high concentrations of fructose in the medium adrenaline also causes an inhibition of the uptake of fructose.3. The mechanism of the adrenaline effect is studied in experiments where the respiration is blocked by the addition of NaCN. The carbohydrate metabolism in the diaphragm then exhibits the following features.a) The uptake of glucose in control experiments is of the same magnitude as under aerobic conditions. Adrenaline inhibits the uptake of glucose on an average by 25 per cent, an effect which is approximately of the same magnitude as the adrenaline effect under aerobic conditions.b) The concentration of hexosemonophosphate is rapidly reduced to 1/10 of the value under aerobic conditions and adrenaline has no effect. This is in contrast to the situation under aerobic conditions where adrenaline effects an accumulation of hexosemonophosphate.4. Adrenaline has no definite effect on the content of inorganic P, ATP or phosphocreatine in the diaphragm.5. Adrenaline produces a slight inhibition of the hexokinase activity in homogenate and extract of the diaphragm with an average value of 10 per cent.6. The present work indicates that the inhibition of the glucose assimilation in muscle by adrenaline is not only due to an accumulation of hexosemonophosphate intracellularly, but can also be attributed to a primary effect of adrenaline on the hexokinase reaction.