Mean values of lead concentrations were 35.68±7.368 ppb in kidneys, 27.95±6.385 ppb in liver and 12.43±4.702 ppb in muscles in animals of treated group. Similarly, the average lead levels were 7.49±1.49 ppb in liver, 7.05±0.69 ppb in kidney and 0.45±0.19 ppb in muscles in animals of control group. Maximum concentration of lead was accumulated in kidney (40.89 ppb) followed by liver (32.46 ppb) and muscles (15.76 ppb) in treatment group, whereas, the maximum concentration of lead was found in liver (8.54 ppb) followed by kidney (7.54 ppb) and muscles (0.59 ppb) in control group (Table 1). The lead accumulation was significantly higher (P≤0.05) in liver and kidneys of treatment group compared to the control.
Table 1: Concentration (ppb) of heavy metals (arsenic and lead) in various tissues of rabbit (Oryctolagus cuniculus).
Mean values of arsenic concentration was 18.70±3.45 ppb in kidneys, 18.01±3.76 ppb in liver and 7.07±2.45 ppb in muscles in animals of treated group. Similarly, the average arsenic levels were 4.21±0.80 in kidney, 2.77±0.62 ppb in liver, while not detected in muscle tissue of control group. Maximum concentration of arsenic was accumulated in kidney (23.64 ppb) followed by liver (21.43 ppb) and muscles (10.23 ppb) in treatment group, whereas, the maximum concentration of arsenic was found to be in kidney (4.78 ppb) followed by liver (3.21 ppb) and below detection limits in muscle (Table 1). The arsenic accumulation was significantly higher (P≤0.05) in kidneys of treatment group compared to the control.
In the present study, it was found that the bioaccumulation of two heavy metals i
. arsenic and lead increased several times in treated animals compared to control animals. Further the concentrations of these heavy metals detected in control group were within the recommended limits. Guideline values recommended for lead and arsenic in drinking water are 0.05 mg/L and 0.005 mg/L respectively (WHO, 1996)
. There are no published data concerning the heavy metals level in tissues of rabbits (Oryctolagus cuniculus
) from Pakistan.
High concentrations of heavy metals have been detected in mammals inhabiting polluted areas (Ma et al., 1991; Świergosz-Kowalewska et al., 2005; Sanchez-Chardi et al., 2009).
Concentration of heavy metals including lead has been measured in liver and muscles of a rodent (Ctenomys talarum
) in areas with different amount of exposure to pollution (Schleich et al., 2010).
The major path of heavy metal exposure in animals is oral consumption (Baker et al., 2003).
Heavy metals then accumulate into different organs of the body (kidney, liver and muscles). Significant levels of lead accumulation have been recorded from muscle tissues of a freshwater and marine fish (Ahmed et al., 2016; Anjum et al., 2019).
Absorbed lead is stored in soft tissues mainly the liver tissues (Lyn-Patrick, 2006)
. In a previous study, lead accumulated at different rates in various tissues of hare (Lepus nigricollis
). The higher concentration was found in kidney and liver while lower concentration was found in muscles (Shahid et al., 2013).
Results of our study coincide with the results of this study.
The lead concentrations in muscle of rabbits in the present study was more than the values recorded in muscles of ruminants in several other studies (Falandysz, 1993; Tahvonen and Kumpulainen, 1994; Doganoc, 1996)
. Higher concentration of lead has been recorded in kidney than in liver (Venalainen et al., 1996).
This was consistent with the findings of our study.
In one study conducted in goats, arsenic was detected at elevated levels in several tissues with significant increase in kidney and liver (Vahter and Marafanate, 1987)
. The maximum concentration was found in liver of goat. Our results were partly in agreement with the reports of Vahter and Marafanate (1987)
in goat, as we found significantly higher concentrations of arsenic in liver and kidney of rabbit. However, the maximum concentration was found in kidney of rabbit though concentration level of arsenic in kidney and liver of rabbit differed only in decimals (Table 1). The mean concentrations of arsenic detected in liver and kidney in rabbits in present study are also in agreement with another study conducted in sheep and goat (Akoto et al., 2014).
Our study shows greater mean value of arsenic in kidney, liver and muscles compared to work of Alonso et al., (2000)
who detected concentrations of three toxic elements i
. arsenic, cadmium, lead in several tissues of liver, kidney, muscle and blood of calves and cows. Whereas, arsenic concentrations in liver, kidney and muscle from cattle in Sweden (Jorhem et al., 1991)
and Australia (Kramer et al., 1983)
were lower than those in the present study. These differences in accumulated concentrations may be due to differences of metals in environment.
Our study revealed that the kidney and liver were the most vulnerable organs to chronic arsenic exposure which was similar to the finding of Al-forkan et al., (2016).
These findings along with several previous studies (Abou-Arab, 2001; Hussein et al., 2013)
demonstrated that the liver and kidneys were the target tissues for monitoring metal contamination in animals. Both organs played key role in removing the toxic metals from the body and therefore ended up accumulating them. It could be concluded that the heavy metals tend to bioaccumulate at relatively higher concentration in tissues with key role in metabolism of toxic substances i
. kidney and liver in rabbit.