Abstract
The effect of adrenergic blocking agents on phosphorylase activation by epinephrine was studied in vitro with diaphragm, heart and liver tissue from the rat.
The stimulation of phosphorylase activity in diaphragm was inhibited completely by dichloroisoproterenol, methoxamine and nethalide. Dihydroergotamine and phentolamine were without effect.
In contrast, phosphorylase activation in the liver was inhibited by dichloroisoproterenol and methoxamine as well as by dihydroergotamine and phentolamine.
Dichloroisoproterenol itself stimulated diaphram phosphorylase at low concentrations. At higher concentrations the drug inhibited its own action.
Methoxamine effectively inhibited the activation of phosphorylase activity by epinephrine in diaphragm, liver and heart. One of the actions of this compound may be that of a β-adrenergic blocking agent.
Ephedrine, at high concentrations, stimulated phosphorylase activity in the rat diaphragm but inhibited the action of epinephrine on the enzyme.
Footnotes
- Accepted April 22, 1964.
- The Williams & Wilkins Comapny
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