There is growing interest in oxytocin as a biomarker of stress and welfare. The objective of this study was to develop and validate a procedure based on a highly sensitive immunoassay to measure oxytocin in the hair of pigs. In addition, a pilot study to apply this procedure to evaluate possible changes in concentrations of oxytocin in hair during the reproductive cycle of pigs at different periods of the year was conducted. This procedure used methanol for sample extraction, since it offered better recoveries than acetonitrile, and the immunoassay developed was precise and accurate for the quantification of the oxytocin in the hair. When this procedure was applied to hair collected at different times of the reproductive cycle and season, higher values were found at days 23 and 59 after farrowing in the winter–spring period. In addition, higher oxytocin values in the spring–summer period were found in hair collected 5 days before farrowing compared to winter–spring. Oxytocin in hair showed moderate and low correlations with cortisone and cortisol in hair, respectively. This study represents the first report in which oxytocin was measured in hair and could open new lines for future research about the measurement of oxytocin in pigs and other biological species as a biomarker of stress.

This study aimed to evaluate the changes in the activity of total salivary alpha-amylase (TsAA) and both the non-glycosylated and glycosylated salivary alpha-amylase proteoforms (NGsAA and GsAA, respectively) in physical and psychological stress models, estimated using a simple and easily set-up method. The method used was a spectrophotometric assay with 2-chloro-4-nitrophenyl-α-D-maltotriose (CNPG3) as a substrate, incubated with Concanavalin A (ConA) to remove most of the glycosylated protein from the sample. This method allowed the measurement of TsAA and estimation of NGsAA and GsAA activities with imprecision lower than 10%. When this method was applied to two different stress models, differences in the responses of the proteoforms were observed, with the NGsAA activity showing changes of higher magnitude after stress induction than the GsAA activity, and the highest correlation with the State–Trait Anxiety Inventory Scale in the Trier Social Stress Test (TSST). In conclusion, the activity of the two main sAA proteoforms can be easily estimated in saliva, and their measurement can provide additional information on TsAA activity in physical or psychological stress situations.

Liver transplantation is commonly used for end-stage liver disease, but the demand for organs exceeds the supply, leading to the use of expanded criteria donors (ECDs). Organs from ECDs, especially from donors after circulatory death (DCD), encounter challenges like increased ischemia damage. Biomarkers, especially oxidative stress markers, may provide valuable insights for understanding and monitoring post-transplant events. Here, we highlight the unique value of organ preservation solution (OPS) as a non-invasive and early source of redox biomarkers, directly reflecting graft status during critical cold storage. This study investigated oxidative stress in 74 donated livers using OPS samples collected after cold storage, and also liver biopsies obtained before and after storage. We measured lipid peroxidation, protein carbonylation, DNA oxidation, and total antioxidant capacity from OPS, and performed gene expression analysis of liver biopsies. Oxidative stress markers differed based on donation type, with higher lipid peroxidation in DCD samples compared with donation after brain death (18.51 ± 2.77 vs. 11.03 ± 1.31 nmoles malondialdehyde (MDA)/mg protein; p = 0.049). Likewise, oxidative damage markers were associated with clinical outcomes: lipid peroxidation was increased in patients who developed biliary complications (21.86 ± 5.91 vs. 11.97 ± 1.12 nmol MDA/mg protein; p = 0.05), and protein carbonylation was elevated in those experiencing acute rejection (199.6 ± 22.02 vs. 141.6 ± 15.94 nmol carbonyl/mg protein; p = 0.005). Moreover, higher protein carbonylation levels showed a trend toward reduced survival (p = 0.091). Transcriptomic analysis revealed overexpression of genes associated with reactive oxygen species production in DCD livers. A predictive model for acute rejection integrating OPS biomarkers with clinical variables achieved 83% accuracy. Hence, this study underscores the importance of assessing oxidative stress status in preservation fluid as a biomarker for evaluating liver transplant outcomes and highlights the need for validation in larger, independent cohorts.