@article {NAMM299, author = {DONALD H. NAMM}, title = {THE ACTIVATION OF GLYCOGEN PHOSPHORYLASE IN ARTERIAL SMOOTH MUSCLE}, volume = {178}, number = {2}, pages = {299--310}, year = {1971}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {The effects of a variety of pharmacologic agents and physiologic ions on the degree of activation of arterial glycogen phosphorylase were studied in the isolated rabbit aortic strip. All procedures which resulted in the development of tension in this smooth muscle also caused an increase in the degree of activation of phosphorylase. Drug-induced relaxation of previously contracted aortic strips was accompanied by a decrease in the activation state of phosphorylase. Cyclic adenosine monophosphate and dibutyryl cyclic adenosine monophosphate in concentrations up to 10-4 M were without effect on either the contractile tension or the phosphorylase activation of the aortic strip. Ca++, a stimulant of skeletal muscle phosphorylase kinase, was shown to activate arterial phosphorylase when the ion was added to the partially depolarized (60 mM K+) aortic strip. The magnitude of drug-induced phosphorylase activation and tension development of the aorta was shown to be a function of the extracellular Ca++ concentration. Furthermore, depletion of tissue Ca++ caused a marked reduction of the drug-induced phosphorylase activation. These results indicate that Ca++ plays an important role in the regulation of phosphorylase activity of arterial muscle. It is proposed that this divalent ion may act as a common mediator of both the mechanical events in the muscle and the activation of this important glycogenolytic enzyme. {\textcopyright} 1971 by The Williams \& Wilkins Co.}, issn = {0022-3565}, URL = {https://jpet.aspetjournals.org/content/178/2/299}, eprint = {https://jpet.aspetjournals.org/content/178/2/299.full.pdf}, journal = {Journal of Pharmacology and Experimental Therapeutics} }