Stimulatory and inhibitory effects of hydrogen peroxide, diamide and vitamin K-5 on sugar transport in rat soleus muscle

Abstract

These experiments examined the stimulatory effects of H 2O 2, diamide and vitamin K-5 on the uptake of d-[U- 14C]xylose by rat soleus muscle. All three oxidants stimulated sugar transport to the same extent, which was 30–40% of the maximal stimulatory effect of insulin (0.1 U/ml). Maximum stimulation was achieved with vitamin K-5 (0.01–0.1 mM), diamide (0.3 mM) and H 2O 2 (5–10 mM); at these centrations the oxidant did not affect muscle ATP levels. Cytochalasin B (5 μM) abolishe doxidant-stimulated xylose uptake. Catalase (20 U/ml) abolished the stimulatory effect of H 2O 2, but did not affect diamide- or vitamin K-5-stimulated transport. The ability of oxidant to stimulate sugar transport in anaerobic muslce could be demonstrated in shor term (30 min) experiments, where muscle contained about 50% of its original ATP, but not after 120 min, when ATP levels were depleted. Oxidant-stimulated sugar transport was diminished and even abolished at supra-optimal concentrations; at these higher concentrations muscle ATP levels were lowered. All three oxidant inhibited the stimulatory effect of 2,4-dinitrophenol on sugar transport; this effect could be demonstrated using those oxidant concentrations which induced maximal stimulation of basal xylose uptake and which did not affect muscle ATP. It is concluded that: (1) H 2O 2, diamide and vitamin K-5 stimulate stereospecific sugar transport in sloleus muscle by some mechanisms other than lowering of ATP levels; (2) stimulation of sugar transport by oxidants in an ATP-dependent process; (3) some oxidant-sensitive sulphydryl group is critically involved in the process which activates muscle sugar transport.