FATE OF INHIBITORS IN THE ANIMAL 



417 



and be inactivated or be lost by renal excretion, both usually occurring 

 simultaneously. The equations are similar to those for the simpler case: 



(I.) = (IJo ^^^7^ [(^1 + -^0 + cc)e'^' - (A-: + h + i5)e«'] (8-15) 



(I.) = (Io)o 



A-, 



« - /3 



|-ga< _ g^ij 



(8-16) 



TIME - 



Fig. 8-4. Variation of intracellular inhibitor concentration with time for diiJerent 



values of the rate constants. (I^,),, = 10 niM. Curve 1: k^ = 1, l\ = 1; curve 2: l\ = 3, 



Z;2 = 1; curve 3: ^'i = 1, ^'2 = 3; curve 4: Ai = 3. ^2 = '^• 



where the constants have the following values: 



a = 1/2 [- (•2A-, + k, + h) - V U; + k; + kl - 2hh] (8-17) 



iS = 1/2 [- Clk, + k, + k,) + ^/Ul +kl + kl - 2U2] (8-18) 



It may be seen by inspection of these equations that (I,) will reach lower 

 values than in circumstances where no excretion occurs and that its rate of 

 decrease will be greater. If, in these equations, A^g is set equal to zero, 



