Pharmacokinetics of difloxacin in olive flounder Paralichthys olivaceus at two water temperatures

Population Pharmacokinetics of Difloxacin in Crucian Carp (Carassius auratus) after a Single Oral Administration

This study aimed to investigate the population pharmacokinetics of difloxacin in crucian carp (Carassius auratus) orally provided a single dose of 20 mg/kg body weight (BW). To achieve this, fish were sampled at various intervals using a sparse sampling strategy, and plasma samples were analyzed using the high-performance liquid chromatography (HPLC) method. Subsequently, naïve average data were analyzed using a non-compartmental method, and a population model was developed based on the nonlinear mixed effects approach. The covariate of BW and the relationship between covariances were sequentially incorporated into the population model. However, it was found that only covariance and not BW affected the population parameters. Therefore, the covariance model was taken as the final population model, which revealed that the typical values of the absorption rate constant (tvKa), apparent volume of distribution per bioavailability (tvV), and clearance rate per bioavailability (tvCl) were 1.18 1/h, 14.18 L/kg, and 0.20 L/h/kg, respectively. Based on the calculated free AUC/MIC values, the current oral dose of difloxacin (20 mg/kg BW) cannot generate adequate plasma concentrations to inhibit pathogens with MIC values above 0.83 μg/mL. Further study should be carried out to collect the pathogens from crucian carp and determine the MIC data of difloxacin against them. Pharmacodynamic experiments must also be further carried out to determine the optimal therapeutic dose for the treatment of Aeromonas hydrophila infection.

Multi-Omics Analysis Provides Novel Insight into Immuno-Physiological Pathways and Development of Thermal Resistance in Rainbow Trout Exposed to Acute Thermal Stress

In recent years, poikilothermic animals such as fish have increasingly been exposed to stressful high-temperature environments due to global warming. However, systemic changes in fish under thermal stress are not fully understood yet at both the transcriptome and proteome level. Therefore, the objective of this study was to investigate the immuno-physiological responses of fish under extreme thermal stress through integrated multi-omics analysis. Trout were exposed to acute thermal stress by raising water temperature from 15 to 25 °C within 30 min. Head-kidney and plasma samples were collected and used for RNA sequencing and two-dimensional gel electrophoresis. Gene enrichment analysis was performed: differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were identified to interpret the multi-omics results and identify the relevant biological processes through pathway analysis. Thousands of DEGs and 49 DEPs were identified in fish exposed to thermal stress. Most of these genes and proteins were highly linked to DNA replication, protein processing in the endoplasmic reticulum, cell signaling and structure, glycolysis activation, complement-associated hemolysis, processing of released free hemoglobin, and thrombosis and hypertension/vasoconstriction. Notably, we found that immune disorders mediated by the complement system may trigger hemolysis in thermally stressed fish, which could have serious consequences such as ferroptosis and thrombosis. However, antagonistic activities that decrease cell-free hemoglobin, heme, and iron might be involved in alleviating the side effects of thermally induced immuno-physiological disorders. These factors may represent the major thermal resistance traits that allow fish to overcome extreme thermal stress. Our findings, based on integration of multi-omics data from transcriptomics and proteomics analyses, provide novel insight into the pathogenesis of acute thermal stress and temperature-linked epizootics.

Pharmacokinetic Behavior of Marbofloxacin in Plasma from Chickens at Different Seasons

The purpose of this study was to evaluate the differences in the disposition and plasma pharmacokinetic behavior of marbofloxacin (MAR) in broiler chickens at different seasons. Chicken broilers (n = 345) were used, in lots of 5 individuals, divided into 6 groups depending on the way of administration, intravenous or oral (dose 2 mg/kg) and the test period. Post-administration plasma samples were obtained at different times, intravenously (0.08 to 24 hours) and orally (0.25 to 120 hours). A liquid-liquid extraction of MAR was performed by high-performance liquid chromatography (HPLC) with a fluorescent detector. The plasma concentrations obtained at the different sampling times of each season, were analyzed with ANOVA and pharmacokinetic analysis was conducted with the PK Solution 2.0 software. The concentration of marbofloxacin in plasma was significantly lower in winter and summer than in spring, with MAR being detected in winter up to 72 hours post-application, coinciding with the differences in MAR pharmacokinetics parameters with increase in the average residence time (MRT) is 9.4 hours in winter. Increased clearance MAR in summer (7.5 ml/min/kg) coincides with MRT 6.3 hours. Finally, the oral bioavailability of MAR is lower in summer and winter (86 ± 1.7% and 78 ± 3.1%) than in spring (94 ± 5.2 %). There are differences in the disposition and plasma pharmacokinetic behavior of MAR applied orally in broiler chickens, coinciding with the physiological changes in the thermoregulation of birds, considering its correct therapeutic management and contributing to provide safe food for human consumption.