Recent reports have shown that stressful situations may affect the production of unconjugated pterins (neopterin and biopterin). The aim of the study was to investigate the effect of castration on neopterin and biopterin plasma concentrations in piglets, using 2 groups of 12 piglets allocated to castrated and uncastrated (control) groups. Pterin concentrations were determined by HPLC with fluorescence detection. Blood samples were also analzyed for leukocyte profiles and plasma cortisol concentrations. A time × treatment interaction was detected for neopterin concentrations, such that neopterin was greater at 1 h after surgery in castrated piglets compared with precastration concentrations, and neopterin was greater in castrated than in control piglets at 1 h. Castration had no effect on biopterin concentration. Time effects for neutrophil and lymphocyte concentrations and neutrophil-to-lymphocyte ratios were found. A time × treatment interaction was detected for plasma cortisol concentrations, such that cortisol was greater at 1 and 24 h after surgery in castrated piglets compared with precastration concentrations and was greater in castrated than in control piglets at 1 and 24 h. This study showed that castration activated the immune system of piglets as demonstrated by an increase in plasma neopterin concentrations.

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