Microsomes obtained from different groups or rats, following
pretreatment with different dosages or 3,4-benzpyrene (BP), aflatoxin
Bl (Bl), ethionine (ET) and/or a combination of these, were used to
obtain initial velocity data for BP disappearance. The values for
Km, Vmax and K/v for different groups were obtained by the computer
analysis of initial velocity data. Vmax and
Km values were used to
assess the quantitative and qualitative changes of microsomal B:2
hydroxylase, respectively, caused pretreatment. BP pretreatment
greatly enhanced the V and also decreased the Km values. The
increase in Vmax paralleled the increase in the dosage of BP from
BP(lX) to BP(3X). When ET, a protein inhibitor, was given in conjunction with BP it blocked the increase in Vmax but did not block
the effect of BP on the Km. The effect of BP on the qualitative
properties (Km) of enzyme was observed to be a slow time dependent
phenomenon which required the simultaneous presence of both the enzyme
and the inducer.