Fuel oxidation in skeletal muscle is increased by nitric oxide/cGMP--evidence for involvement of cGMP-dependent protein kinase.

The cyclic guanosine-3',5'-monophosphate (cGMP) analogue, 8-bromo-cGMP (1 mM), increased glucose oxidation in isolated soleus muscle. The nitric oxide (NO) donor, sodium nitroprusside (SNP) (15 mM), increased glucose, pyruvate, palmitate and leucine oxidation. Removal of extracellular Ca2+ did not affect SNP-stimulated glucose oxidation (or other glucose utilization parameters), thus eliminating the influx of Ca2+ as a mechanism for the increases. The guanylate cyclase inhibitor, LY-83583 (10 microM), inhibited SNP-stimulated palmitate oxidation and activation of cGMP-dependent protein kinase (PKG). Activation of PKG might supersede any inhibitory effects of NO on respiration to stimulate metabolic fuel oxidation in skeletal muscle.