Effects of dietary vitamin A on antioxidant responses of abalone Haliotis discus hannai Ino

A 240 d growth experiment was conducted in a re-circulated water system to investigate the effects of dietary vitamin A on growth and antioxidant responses of abalone Haliotis discus hannai Ino.Triplicate groups of juvenile abalone[initial mass was (0.96±0.02) g, shell length was (17.70±0.06) mm] were fed to satiation one of three semi-purified diets containing 0, 1×10³, 1×10⁶ IU vitamin A per kilogram diet, respectively.Results showed that the daily increment in shell length (DISL) of abalone in the treatment with 1×10³ IU vitamin A per kilogram diet was significantly higher than that with 0 or 1×10⁶ IU vitamin A per kilogram supplementation (P> 0.05).Vitamin A deficiency (0 IU/kg) significantly elevated the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione reductase (GR) in the viscera of abalone (P> 0.05).In muscle, the effects of vitamin A deficiency on SOD and GPX activities were the same as those in viscera, however, the activity of GR significantly decreased (P> 0.05).Vitamin A deficiency significantly decreased the ratio of CAT to SOD (catalase/superoxide dismutase) in viscera (P> 0.05).Nevertheless, it significantly decreased the ratio of GR to GPX in muscle (P> 0.05).Compared with the supplement of 1×10³ IU vitamin A per kilogram, excessive vitamin A (1×10⁶ IU/kg) had no significant effects on the activities of CAT, SOD and glutathione-S-transferase (GST) (P> 0.05), but significantly elevated GPX and GR activities in viscera (P> 0.05).In muscle, the activities of CAT, SOD, GPX, GST and GR were significantly decreased by the excessive dietary vitamin A supplement (P> 0.05).Compared with the supplement of 1×10³ IU vitamin A per kilogram, vitamin A-excessive had no significant effect on the value of ratio of CAT to SOD either in viscera or in muscle (P>0.05).The ratio of GR to GPX was significantly decreased in viscera, but significantly elevated in muscle in the vitamin A-excessive group (P> 0.05).In conclusion, optimum supplement of vitamin A (1×10³ IU/kg) was beneficial for abalone to maintain maximum growth and antioxidant system.Hypo-or hyper-vitaminosis A would decrease growth and the efficiency of scavenging reactive oxygen species (ROS) of abalone.