Effect of dietary resveratrol on cell-mediated immunity and hepatocyte morphometry in the model organism medaka (Oryzias latipes Temminck & Schlegel)

The effect of dietary resveratrol (40 µg g⁻¹ BW day⁻¹) on cell-mediated immunity (the activity of spleen phagocytes and the proliferative response of lymphocytes) and liver histology (hepatocyte morphometry, lipid vacuoles, and glycogen granules) in adult medaka (Oryzias latipes) (aged two years, body weight BW = 0.49 g) were tested after ten days of feeding with experimental diets. The fish were fed either a commercial diet (control group C) or this same diet supplemented with resveratrol (group R) three times daily at 3% of body weight (BW). Fish fed feed with resveratrol had significantly higher intracellular phagocyte killing activity than did those in the control group (P < 0.05). No differences in the sizes of hepatocytes or their nuclei were observed in the fish from groups C and R. The nucleo-cytoplasmic ratio ranged from 0.39 (± 0.03; group R) to 0.42 (± 0.03, group C) in adult medaka exposed to the two dietary treatments (P > 0.05). The results indicated that the diet supplemented with resveratrol at a dose of 40 µg g⁻¹ BW day⁻¹ had no impact on the liver tissues. Typical hepatocytes with lipids and glycogen were observed to the same extent in the vacuoles. Moreover, no mortality or pathological changes were noted in the fish studied. The diet containing resveratrol helped to maintain disease resistance without affecting the liver tissue after ten days of feeding.