To determine whether nitric oxide (NO) synthase activity exists in rat skeletal muscle, media from incubated rat extensor digitorum longus muscle preparations were assayed for NO with a chemiluminescent detection system. Although small amounts of NO were detected in media alone, the addition of muscle increased NO concentration in the media by 30-fold. The release of NO into the media diminished over time. Either arginine (10(-6) M), sodium nitroprusside (10(-6) M), or prior electrical stimulation in vivo caused 50-200% increases (P < 0.05) in NO concentration. NG-monomethyl-L-arginine monoacetate (10(-6) M), an NO synthase inhibitor, decreased both basal 2-deoxyglucose transport and NO efflux, indicating that NO may play a role in modulating skeletal muscle carbohydrate metabolism. These data indicate that NO is released from an incubated skeletal muscle preparation and presents the possibility that muscle-derived NO may play an important metabolic role.