One of the first investigations dealing with the effects of coexposure
to Pb and Cd on liver functions in vivo and further on
oxidative status was conducted by Gupta’s group who treated female
rats i.p. with the same doses of Pb and/or Cd: 0.05 mg Pb-acetate,
0.05 mg Cd-acetate, or combination of 0.025 mg Pb-acetate and
0.025 mg Cd-acetate for 15 days. Lead induced a decrease in the activity
of SOD in liver, while the same dose of Cd caused more
pronounced effects on parameters of oxidative stress: the reduction
of SOD activity was greater, and furthermore, GSH levels were
depleted and CAT activity and TBARS levels were increased. The coexposure
produced effects which were similar to the effects of Cd
given alone in all investigated parameters, while the total concentration
of metals in liver after combined treatment was not
significantly different from the individually treated groups. Hence,
the authors concluded that when Pb and Cd were given i.p. in similar
concentrations, Cd was the one that predominantly affected oxidative
status due to its more reactive nature (Pillai and Gupta, 2005).
Pandya et al. (2010) continued with same model of experiment, but
using 2-fold lower doses. The accumulation of both metals in liver
when given in a mixture was decreased compared with groups
exposed to a single metal, and this decrease was more prominent
in the case of Cd, indicating interactions between these two metals
in liver. In this experiment, more profound effects on parameters
of oxidative stress (with the exception of GPx activity) were observed
in the group treated with Cd only, indicating possible
antagonism between Cd and Pb on oxidative stress induction in liver.
This antagonism resulted in lower levels of hepatic Cd in the cotreated
group inducing less pronounced effects on oxidative status.
These findings are in accordance with proposed more reactive nature
of Cd in producing oxidative stress in comparison to Pb.