Temporal relationship between the levels of melatonin and different antioxidants in the liver of a surface feeding carp Catla catla

Abstract

ABSTRACTPresent study provided the first information on temporal relationship between melatonin concentrations and oxidative status of the liver in any fish. Accordingly, the liver tissue homogenates of carp Catla catla were used to measure the diurnal levels of melatonin, malondialdehyde (MDA) – an intra-cellular stress marker, and different antioxidants [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GRd), glutathione S-transferase (GST), reduced glutathione (GSH)] during four distinct reproductive seasons of an annual cycle. The hepatic melatonin titres exhibited significant daily variations with a peak in early dark-phase and nadir at midday in each season, though its diurnal values were highest in post-spawning phase and lowest during spawning. Likewise, the activities/levels of different antioxidants, other than GSH, displayed diurnal peak in early dark-phase and seasonal peak during post-spawning phase. The hepatic MDA levels were diurnally maximum in midday, and seasonally highest during spawning and lowest in post-spawning phase. Although hepatic melatonin titres were positively correlated with the levels of each antioxidant, MDA levels were negatively correlated with the levels of both melatonin and each antioxidant. Collectively, current study underlines possible influences of endogenous hepatic melatonin on the oxidative status of liver relating to seasonal reproductive events in a fish species.