The effect of β-receptor blockade on adrenaline-induced changes in redox and energy state in m. vastus lateralis and m. soleus of the rat in vivo

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Abstract
The metabolic changes in blood, red (m. [musculus] soleus) and white (m. vastus lateralis) skeletal muscle fibers were investigated after short-term (3 min) infusion of adrenaline [epinephrine] with or without prior treatment with propranolol or metoprolol. The adrenaline-induced increase in plasma lactate levels was totally prevented by prior treatment with metoprolol or propranolol; the .beta.-blockers had no effect on blood glucose levels. Similar effects on lactate levels were found in the m. soleus, while metoprolol was less effective than propranolol in m. vastus lateralis. Adrenaline decreased the level of muscle creatinine phosphate and ADP, causing the equilibrium of the creatinine kinase reaction to change in the direction of ATP synthesis, although the level of ATP usually decrease. This effect was more pronounced in m. vastus lateralis compared with m. soleus. The [ATP]/[ADP] [Pi]-ratio tended to increase during infusion of adrenaline. This effect was counteracted by metoprolol but not by propranolol. The effects on the phosphate potential ([ATP]/[ADP] [Pi]) and the equilibrium within the creatine kinase were more pronounced in m. vastus lateralis than in m. soleus. The possible role receptors other than .beta.-receptors, i.e., .alpha.-receptors, in mediating changes in plasma glucose levels are demonstrated; plasma lactate levels are regulated by the .beta.-adrenergic system. The role of .beta.-receptors in mediating changes in muscle lactate levels may differ in m. soleus and m. vastus lateralis, with a relative predominance of .beta.2-receptors in m. vastus lateralis. Quantitative and qualitative differences in the adrenergic control of the energy state in the 2 types of muscle fiber were obvious, although it was not possible to distinguish clearly between the relative importance of .alpha., .beta.1 and .beta.2-receptors.