Influence of Manganese on Growth, Somatomedin and Glycosaminoglycan Metabolism

Day-old chicks were fed control or manganese (Mn)-deficient diets ad libitum for 25 d. The chicks subsequently were refed control diet for up to 5 d. Mn deficiency significantly decreased growth rate and feed intake compared to controls. After 25 d of depletion, bone Mn concentration was 2% that of controls and 88% of the deficient chicks exhibited signs of perosis. Sulfate (35SO4) uptake into uronic acid was significantly depressed in cartilage from the Mn-depleted chicks and increased rapidly with refeeding, which may indicate increased glycosaminoglycan (GAG) biosynthesis or increased sulfation of the GAG molecule. In vitro activity of glycosyltransferases suggest that GAG synthesis may be interrupted by Mn deficiency. Somatomedin activity, serum insulin and glucose levels were not influenced significantly by Mn deficiency. Thus, while Mn deficiency decreased growth and GAG synthesis, these effects were not mediated by somatomedin.