Active transport of sodium and potassium in mammalian skeletal muscle and its modification by nerve and by cholinergic and adrenergic agents.
1. Active transport of Na(+) and K(+) by Na-rich extensor digitorum and soleus muscles of rat was found to be increased considerably when muscles were innervated during enrichment with Na(+) in K-free modified Krebs solution containing 160 mM-Na at 2 degrees C and recovery in a similar fluid with 10 mM-K and 137 mM-Na at 37 degrees C, bubbled with oxygen.2. Addition of acetylcholine (2.0 mug/ml.) to recovery fluid containing denervated extensors increased active transport, whereas addition of eserine (50 mug/ml.), decamethonium (0.1 mug/ml.) and to a lesser extent tubocurarine (0.26 mug/ml.) inhibited active transport. Blocking of nerve conduction in innervated extensor inhibited K(+) uptake more than Na(+) excretion.3. The membrane potential of Na-rich extensor muscles measured soon after re-immersion in recovery fluid was higher in denervated than in innervated muscles. In the latter it was close to the K-equilibrium potential (E(K)). It is suggested that denervation here makes the Na-pump electrogenic by decreasing K(+) uptake either by decreased permeability or by inactivating a K-pump. Evidence is presented that the latter is more likely.4. Addition of isoprenaline to Na-rich soleus muscles in recovery fluid increased active transport and reduced the membrane potential measured soon after re-immersion in recovery fluid. The Na-pump still remained electrogenic in the presence of isoprenaline. It was suggested that isoprenaline might also stimulate the Na-pump, perhaps through activation of lactic dehydrogenase.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects*; D003650:Decamethonium Compounds / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology*; D009121:Muscle Denervation; D009132:Muscles / Q000294:innervation* / Q000378:metabolism*; D009431:Neural Conduction; D010830:Physostigmine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D014403:Tubocurarine / Q000494:pharmacology
D003650:Decamethonium Compounds; D012964:Sodium; D010830:Physostigmine; D007545:Isoproterenol; D000109:Acetylcholine; D011188:Potassium; D014403:Tubocurarine