*4.2. Animals and Experimental Design*

Thirty Specific-Pathogen-Free (SPF) mice (Kunming mice, 25–35 g) were obtained from Changsha Tianqin Biotechnology Co., Ltd. (Changsha, China), and the animals were maintained at the Guangdong Ocean University Animal Centre under light (12 h of light and dark) and temperature (~25 ◦C). The animals were given a standard laboratory diet and water. The experiment was approved by the Animal Ethics Committee of Guangdong Ocean University (No.: GDOU-LAE-2020-009). The animals were randomly divided into 5 groups (*n* = 6). Control group: Intraperitoneal injection of 0.9% NaCl (saline) once daily. Cd-exposed group: the mice were injected intraperitoneally with CdCl2 5 mg/kg daily [87]. EDTA-treated group (positive control): the mice were injected with CdCl2 (5 mg/kg) intraperitoneally after 1 h of oral administration with EDTA (100 mg/kg) daily. The low dose of OPs(L-OPs)-treated group: the mice were injected with CdCl2 (5 mg/kg) intraperitoneally after 1 h of oral administration with OPs (100 mg/kg) daily. High dose of

OPs (H-OPs)-treated group: the mice were injected with CdCl2 (5 mg/kg) intraperitoneally after 1 h of oral administration with OPs (300 mg/kg) daily. It has been shown that ethylenediaminetetraacetic acid (EDTA) can alleviate cadmium toxicity by enhancing antioxidant enzyme activity and inhibiting inflammatory responses [88]. Therefore, it can be used as a positive control. The doses of EDTA and OPs were determined based on previous studies [89,90]. After 7 days, the mice were executed by cervical dislocation, and the liver was stored at −80 ◦C for further analysis.
