Influence of Anoxia and Dinitrophenol on the Phosphorylase a Activity and the Cyclic Nucleotide Content of Smooth Muscle

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Abstract
The effect of anoxia or 2,4-dinitrophenol (DNP) on the phosphorylase activity and the cAMP and the cGMP content was studied in smooth muscle preparations. When the aerobic conditions were changed to anaerobic in experiments on bovine mesenteric artery, there was a significant increase in the activity of phosphorylase a during the first 60 min. A reduction of the glycogen content of the artery was observed during this time period, which accounted for about 2/3 of the increase in lactate production (Pasteur effect). Under anaerobic conditions the content of cAMP in the vessel was not changed, and the increase in phosphorylase a activity was not inhibited by a blockade of adrenergic .beta.-receptors. DNP, which like anoxia inhibits the mitochondrial production of ATP, increased the phosphorylase a activity to the same extent as anoxia. Anoxia and DNP also enhanced the activity of phosphorylase a in pig thoracic aorta and rabbit colon smooth muscle. In thoracic aorta both anoxia and DNP produced a more transient and smaller increase in the phosphorylase a activity than in the mesenteric artery. The Pasteur effect was also relatively smaller (100%) in thoracic aorta than in mesenteric artery (400%). Evidently, an anoxic increase in the phosphorylase a activity participates in the Pasteur effect in smooth muscle.