Abstract
Abstract 1. 1. The effects of electrical stimulation of the autonomic nerves on glycogen phosphorylase (α-1,4-glucan: orthophosphate glycosyltransferase, EC 2.4.1.1) and on glucose-6-phosphatase ( d -glucose-6-phosphate phosphohydrolase, EC 3.1.3.9) of rabbit liver were investigated. The activities of these two enzymes increased markedly after stimulation of the splanchnic nerve (sympathetic), and the effect was not eliminated by adrenalectomy or pancreatectomy of the rabbits. 2. 2. The response of the enzymes reached a maximum within 30 sec after the onset of splanchnic-nerve stimulation, and the half-time of the increase was approximately 14 sec. 3. 3. The effect of splanchnic-nerve stimulation was completely counteracted by simultaneous stimulation of the vagus nerve (parasympathetic), although vagal stimulation alone had little effect on the enzymes. 4. 4. The dephosphophosphorylase and dephosphophosphorylase kinase (ATP: dephosphophosphorylase phosphotransferase, EC 2.7.1.38) from rabbit liver were partially purified and their properties were studied. 5. 5. Total phosphorylase of the liver was determined by assaying phosphorylase activity after conversion of dephosphophosphorylase to the active form. The total amount of phosphorylase was not altered significantly by splanchnic-nerve stimulation or vagal stimulation. In the resting state, about one fourth of the total phosphorylase in the liver was active. The amount increased to three fourths of the total after stimulation of the splanchnic nerve, but was unchanged during vagal stimulation. 6. 6. Previous treatment of the rabbits with actinomycin S failed to block the increase in phosphorylase activity after splanchnic-nerve stimulation. These results indicate that the increase in phosphorylase activity caused by splanchnic-nerve stimulation can be attributed to enzymic conversion of the dephosphophosphorylase to the active form during stimulation.
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