The effect of food deprivation and refeeding on the liver, thyroid hormones and transthyretin in sea bream

Abstract

There was a significant reduction in body weight of sea bream Sparus aurata and the hepatosomatic index after 3 weeks food deprivation. Liver biochemical indices and morphology were altered by food deprivation, there was a loss of eosin staining in hepatocyte cytoplasm and the appearance of large depleted vacuoles. Cell and nuclear area were significantly reduced (P<0·001) and did not return to control values after 1 week of refeeding. The water, lipid, glycogen and protein content of the liver was significantly reduced by 3 weeks fasting but recovered rapidly after 1 week refeeding. Food restriction also had a marked effect on circulating thyroid hormones and the concentration of plasma T3 (33·98 12·47 ng ml 1) and T4 (16·54 9·5 ng ml 1) was significantly (P<0·001) lower than the control (66·52 13·4 and 56·83 7·3, respectively). Refeeding for 1 week restored circulating T3 (P<0·05) close to control levels but did not significantly affect the concentration of T4. Northern blotting with an homologous probe for transthyretin (TTR) demonstrated clearly the expression of a single mRNA transcript of 0·7 kb for this protein in the liver. The level of TTR message was substantially reduced below control levels in the liver of fasted fish and 1 week refeeding failed to restore expression.