We analyzed the effects of levamisole on stress and the innate immune responses of pacu (Piaractus mesopotamicus). A total of 300 fish (180 ± 1.27 g) were fed a diet containing levamisole hydrochloride (LHC) for 15 days, then distributed into the following groups: T0 (control group); T1 (100), T2 (150), T3 (300) and T4 (500) mg kg LHC (15 fish per group and four replicates per treatment). After this, fish (n = 8 per treatment) were exposed to air for three minutes to simulate stress conditions and were then challenged with the bacterium Aeromonas hydrophila to stimulate the immune system. Fish were sampled at 1, 3 and 24 h after bacterial inoculation to measure plasma cortisol and glucose concentrations, the leukocyte respiratory burst (LRB), hemolytic activity of the complement system (HAC) and serum lysozyme activity (SLA). LHC attenuated the increase in plasma cortisol at 1 h (500 mg kg) and 3 h (300 mg kg) after air exposure and bacterial inoculation compared to control fish. The highest glucose concentrations were observed at 1 and 3 h after stress, which then returned to initial levels after 24 h, without any effect of LHC. The LHC 100 mg kg dose increased LRB 1 h after inoculation and activated the HAC 3 h later. At 24 h, all LHC concentrations increased the HAC. SLA was reduced after inoculation, throughout the experimental period, without an effect of levamisole. Our results indicate that the oral administration of levamisole for 15 days modulated circulating cortisol levels during the stress response and improved the innate immune response against A. hydrophila infection in pacu.
Juveniles de Piaractus brachypomus (30 ± 4,76g) fueron alimentados ad libitum durante 30 d con una dieta de 32 % de proteína, suplementada con seis cantidades diferentes de ácido ascórbico (AA): T1 = 0 mg/kg; T2 = 100 mg/kg; T3 = 200 mg/kg; T4 = 400 mg/kg; T5 = 800 mg/kg; T6 = 1600 mg/kg. Finalizada la fase de alimentación, los animales estuvieron en exposición aérea durante 60 s y luego se devolvieron al agua. Se colectó sangre mediante punción en la vena caudal de tres individuos por tratamiento a los 5; 30; 60 y 360 min después de haber sido devueltos al agua. Con estas muestras se determinaron en plasma las concentraciones de cortisol, glucosa, lactato y proteínas totales. En suero, se midió la concentración de los iones Cl– y Na+. Finalmente se calculó la sobrevivencia. Los datos fueron sometidos a un análisis de varianza ANAVA, y cuando se encontraron diferencias, las medias se compararon mediante prueba de Tukey (α = 0,05). El cortisol presentó el pico más alto en los ejemplares alimentados con la dieta libre de AA. Las concentraciones de glucosa fueron menores en los peces suplementados con 400 mg/kg a los 5, 30 y 60 min. Las concentraciones de los dos iones se mantuvieron estables a través del tiempo en los ejemplares suplementados con 200 mg/kg. La supervivencia fue de 100 % en todos los tratamientos. La suplementación con concentraciones entre 100 y 400 mg/kg AA mejoró la respuesta de los animales ante el estrés por hipoxia.
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