Über die Bedeutung der Adenylsäure für die Muskelfunktion. 2. Mitteilung: Die Desaminierung der Adenylsäure durch Muskelbrei und die Ammoniakbildung bei der Muskelkontraktion.
2. The quantity of NH3 formed by frog and rabbit muscle brei in the presence of NaHCO3 is increased by addition of adenylic acid; the increment being equivalent to 80% of the added substance in 3-4 hrs. Muscle contraction leads invariably to increased muscle NH3 values. Muscular activity and N metabolism are therefore directly related.[long dash]3. The NIL content of resting frog muscle and the increment in activity depend on the species of frog and the season; higher environmental temperatures giving higher basal levels and greater increases on activity. NH3 values decrease rapidly during rest. The ratio of lactic acid to ammonia formed by stimulation of isolated gastrocnemii is far from constant.[long dash]4. The quantity of NIL formed in isolated frog muscle by a given number of excitations is greater as the frequency of stimulation is increased. NIL formed during activity disappears during rest. In slow stimulation, therefore, the NIL may be utilized, in resynthesis of its precursor, almost as rapidly as it is formed. Thus there can be no constant NH3: lactic acid ratio.[long dash]5. Extracts of stimulated and resting frog and rabbit muscle were treated with copper sulfate and lime suspension. The N of the ppt. plus NEL-N present gives a value of 5 times the NH3-N formed on prolonged stimulation. Thus the source of NIL must be a substance containing 1/5 of its N in a form readily split off. As adenine, guanine, gua-nylic acid, and guanosine do not yield NH3, and adenosine has not been found in muscle, adenylic acid must be the precursor of muscle NH3.