The effect of manganese ingestion, phosphate depletion, and starvation on the morphology of the epiphyseal growth plate. A stereologic study.

Oral administration of manganese to young rats results in poorly mineralized primary spongiosa and an irregularly thickened growth plate with a histologic resemblance to that in vitamin D-deficiency rickets. In the present study, the rachitic lesions were characterized by stereologic methods at the light microscopic level. With increasing doses of Mn in the diet, the animals developed rachitic lesions of increasing severity, i.e., the total height of the growth plate and the relative volume of the hypertrophic zone increased. The experimental animals developed hypophosphatemia, which was dependent on the Mn dose. The observed serum concentrations of Mn and phosphorus are compatible with the idea that MnHPO4 is precipitated in the gut, leaving only small amounts of Mn and phosphate available for absorption. Furthermore, the severity of the rachitic lesions were inversely correlated to the concentration of phosphate in serum. The most important pathomechanism in Mn rickets is phosphate depletion, which per se causes similar rachitic changes, even though Mn also seems to have other effects. Starvation caused a decrease in the height of the growth plate and in the volume fraction of the hypertrophic zone, thus changes contrary to the rachitic lesions.