2.6 Collection of biological samples and determination of biomarkers
Fasting blood, spot urine, and hair samples were collected from participants on the morning of recruitment day. Blood samples were saved on ice and transferred to the clinical laboratory of Shimen Central Hospital for routine measurement. Urine samples were collected into cleaned conical 50 ml polypropylene tubes, and packed into coolers with frozen ice packs. Hair samples were saved in envelops and transferred to Shimen Center for Disease Control and Prevention for measurement. Blood arsenic and urine arsenic were analyzed in the laboratory of Tongji School of Public Health, Huazhong University of Science and Technology by inductively coupled plasma-mass spectrometry (Agilent 7700X, USA). Hair arsenic concentration was determined by nondispersive atomic fluorescence spectrometry (Ruiguang RGF-7800, China). Details could be found in our previous paper15.
For human participants, serum levels of pruritic biomarkers were determined by ELISA, following the manufacturer’s instructions for commercial kits of β-endorphin (BSK00470, Bioss), substance P (BSK00600, Bioss), nerve growth factor (BSK00127, Bioss), histamine (BSK00598, Bioss), interleukin-31 (BSK00467, Bioss), IgE (BSK00568, Bioss), endothelin-1 (BSK00345, Bioss), and 5-hydroxytryptamine (BSK00601, Bioss). For mice, β-endorphin was measured using an ELISA kit (0557M1, Meimian). All standards and samples were run in duplicate, and the values were within the range of acceptable variability according to the kit’s standards.