860 15. EFFECTS OF VARIOUS FACTORS ON INHIBITION 



of the rate, but otherwise it will vary. If we designate the sensitive fraction 

 by fg and the resistant fraction by /^, and if an inhibitor produces an inhi- 

 bition of degree i on the sensitive fraction, the following may be written: 



Uninhibited: /« + /r = 1 



Inhibited: (1 — i)fs + fr = relative rate 



. fs 



fs + fr 



ifs (15-125) 



If now the total rate is altered and the individual fractions are changed 

 by the factors n and m: 



(15-126) 



where r is the new rate relative to the initial rate. The ratio of the over-all 

 inhibitions for the two situations is then: 



4^ = — (15-127) 



which is the ratio of the change in the inhibitor-sensitive fraction to the 

 change of the total rate. The observed inhibition can thus either increase 

 or decrease. It is probably more common for the inhibitor-resistant frac- 

 tion to remain at a constant level — i.e., for an increase in over-all rate, n 

 will be greater than m, and since n is also greater than r, the inhibition will 

 increase. The effect in any case will depend on how the rate is changed, 

 since conceivably any relative change in the individual fractions is possible. 



When a tissue becomes more functionally active, the metabolism usually 

 increases, particularly the oxidative and phosphorylative processes, al- 

 though synthetic reactions may also accelerate. The character of the me- 

 tabolism is generally modified so that the inhibitor-sensitive and inhibitor- 

 resistant portions do not change equally. Consequently, an active tissue is 

 often inhibited differently than a relatively resting tissue, as has been dis- 

 cussed in Chapter 9. The inhibition of such systems may be said to depend 

 on the over-all metabolic rates, but actually it is dependent on the pattern 

 of the metabolism and not directly on the rate. 



It has been frequently stated that an active tissue is more readily in- 

 hibited or damaged than a tissue that is less active. However, it is not 

 entirely related to the level of activity but to the metabolic requirements 

 also. If a tissue needs a certain rate of metabolism to maintain a specified 



