Effect on Serum Parameters and Immune Responses of Carassius auratus gibelio Exposed to Dietary Lead and Bacillus subtilis.

Lead (Pb), a heavy metal and an environmental stressor, may affect many physiological processes, including the serum index and the immune response. The aim of this study was to explore the toxic effects of Pb on the serum index and the immune response of Carassius auratus gibelio (C. gibelio) fed 0, 120, or 240 mg/kg Pb, and 10 cfu/g Bacillus subtilis (B. subtilis). After 15 and 30 days of dietary exposure, the serum indices and the immune responses of the fish were assessed. Dietary Pb exposure significantly affected various components of the serum index, including calcium, magnesium, glucose, cholesterol, total protein, glutamic-pyruvic transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH). However, sIgA activity in the gut increased significantly following B. subtilis supplementation. Notable changes were also observed in the expression levels of immune-related genes, including HSP70, IgM, HSP90, IL-1β, IL-6, and TNF-α. B. subtilis supplementation effectively attenuated the effects of dietary Pb exposure.