Abstract
Cd is one of the most common pollutants in the environment that also induces the apoptosis. To explore the mechanism of apoptosis in the hepatopancreas, freshwater crab S . henanense were treated with 0, 3.56, 7.12, 14.25, 28.49 and 56.98 mg/L Cd for 72 h. Apoptosis was noticeable in every treatment group and necrosis was observed clearly in the high concentration Cd groups. Classical apoptotic bodies were found by transmission electronic microscopy, which revealed chromatin condensation under nuclear membrane and mitochondrial membrane rupture. An increasing number of autolysosomes, damaged rough endoplamic reticulum and Golgi complex were observed as the Cd concentration increase. Brown colored apoptotic cells were detected by the TUNEL test in all Cd-treatment groups. The apoptosis index increased following the elevation of Cd concentration and got 32.9% in the highest Cd group. Caspase-9 and caspase-3 activities increased in the lower Cd treatment groups but no changes in the higher Cd concentration groups (comparing to the control group). The activity of caspase-8 did not change significantly. No significant change in the content of mitochondrial cytochrome c (cyt c) in Cd exposed groups except the decrease in the 56.98 mg/L group. In crabs treated with 3.56, 7.12 and 14.25 mg/L Cd, hyperpolarization of mitochondrial membrane potential (Δψ m) significantly increased. These results implied that apoptosis in the hepatopancreas induced by Cd occurrs through the mitochondrial caspase-dependent pathway. However, whether there are other apoptotic pathways needs to be studied further.
Highlights
Cadmium (Cd) is a widespread environmental pollutant worldwide, which is discharged into the environment due to industrial, agricultural and urban activities
In crabs exposed to the lower Cd concentrations, the epithelia were slightly damaged with dots of broken or swollen cells, maintaining, the tissue structure (Figure 1 B)
Cellular swelling and necrosis apparently emerged as the Cd concentration increased
Summary
Cadmium (Cd) is a widespread environmental pollutant worldwide, which is discharged into the environment due to industrial, agricultural and urban activities. Since Cd is not degraded in the environment, it enters the body of animals and humans by respiration [1], occupational exposure and gastrointestinal absorption [2] and gets biomagnification through the food web [3]. Cd ions exert their toxic effects on tissues and cells where they are absorbed. High concentrations of Cd were reported in invertebrates such as oysters and other bivalve mollusks and crabs [6]. The content of Cd in crabs surpassed the maximum standard for Cd in crustaceans
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