In plants and animals, growing tissues and growth zones generally contain more H2O2 and are more oxidized than non-growing tissues (Corcoran et al. , 2013, FEBS J. 280, 944). Therefore, we proposed the hypothesis that growth is connected to increased tissue oxidation also in Atlantic salmon.
In the first study, s almon post-smolts, which had been fed two levels of vitamins C+E, were implanted with growth hormone (GH) and held alongside an untreated control group on the two diets for 42 d ays. Figure 1 shows that t he levels of antioxidant vitamins in the fish tissues followed a dose response to the dietary levels and were reduced in response to GH. Several genes which regulate redox metabolism were modulated by GH, especially in fish fed the low vitamin levels. This indicates that the high vitamin level protected against the oxidative effect of GH (Yin et al., 2022, Antioxidants, 11, 1708 ).
In the second study, salmon post-s molts were exposed to a natural simulated photoperiod during spring. This led to increased growth, consumption of antioxidant vitamins , more cataracts and increased tissue oxidation, as indicated by relevant enzyme activities and the redox transcriptome . Temperature was constant at 9ºC, thus the change in photoperiod alone induced the physiol ogical changes which lead to tissue oxidation and growth stimulation (Yin et al., 2023, Antioxidants, 12, 1546).
These studies support the hypothesis that growth is connected to oxidation in tissues of Atlantic salmon post-smolts . It is important to supplement enough antioxidant vitamins in periods of rapid growth , to balance oxidative stress. Perhaps other antioxidants, for example polyphenols from plant extracts, can help alleviate such oxidative challenges, but this needs to be further elucidated.