498 5. QUINONES 



EFFECTS ON TISSUE FUNCTIONS 



The actions of the quinones on tissues are quite complex in most in- 

 stances, as would be expected from the many possible mechanisms by which 

 these substances can alter metabolism, but nevertheless some interesting 

 results have been reported and should stimulate further investigation along 

 certain lines which may be evident in the following discussion. 



Skeletal Muscle and the Neuromuscular Junction 



Baglioni (1905) showed that 0.23 mM 2>-benzoquinone applied directly 

 to frog muscle causes clonic spasms, and p-benzohydroquinone, which is 

 readily oxidized, is almost as active, whereas phenol, which is not so oxi- 

 dized, is inactive. The question arose as to the necessity for the diphenols 

 to be oxidized before exerting their characteristic toxic actions on tissues; 

 if this is the case, the activity would depend on the rate at which the di- 

 phenol is oxidized under the experimental conditions. Labes (1929 a) 

 undertook to settle this question by the application of 0.9 mM p-benzo- 

 hydroquinone to frog gastrocnemius aerobically and anaerobically. The 

 muscle went into contracture in 15 min in the presence of oxygen, while 

 in the absence of oxygen it shortened much more slowly and to a lesser 

 degree. Furthermore, altering the pH gave results indicating that these 

 effects on muscle to a large extent depend on the rapidity of hydroquinone 

 oxidation, the activity increasing with the pH. Thus the more active form 

 appears to be the quinone. Hinteregger (1930) confirmed and extended 

 these observations. 2>-Benzoquinone was found to act rapidly on frog muscle, 

 quinhy drone more slowly, and p-benzohydroquinone still more slowly. 

 Increasing the pH from 5.8, where there is no action of the hydroquinone, 

 to 8.5 markedly increases the effect, while oxidation of the hydroquinone 

 catalytically with Mn++ also accelerates its action. Muscles obtained from 

 hyperthyroid frogs are more susceptible to the effects of p-benzohydro- 

 quinone, which might be interpreted as due to the more rapid oxidation 

 to the quinone in such muscle, or, as Hinteregger also suggested, to an 

 increased permeability, which could not be experimentally demonstrated. 

 On the other hand, it is quite possible that muscles with a higher metabolic 

 rate might go into contracture faster, this being independent of hydroqui- 

 none oxidation or permeability. It is likely that both the quinone and hy- 

 droquinone forms exert effects on muscle. Sterin (1935) found that resor- 

 cinol, which cannot be oxidized directly to a quinone, produces convulsive 

 twitches of the gastrocnemius muscle, an action very similar to that by 

 p-benzohydroquinone. js-Benzoquinone, on the other hand, tends to produce 

 contracture, so that somewhat different actions may be associated with 

 the two forms. It is tempting to relate the quinone-induced contracture 

 to reaction with SH groups and to compare it with the Lundsgaard effect 



