Influence of Vitamin D on Synthesis of Hexosamine by Rachitic Rat Cartilage

Abstract

IT is believed that chondroitin sulphate or its protein complex plays a very important part in the process of calcification¹. The fact that during calcification there is a marked increase in metachromatic staining in the region which exhibits calcification led Rubin and Howard² to postulate that either there is an increase in the concentration of the mucopolysaccharide or that there is a change in its state of polymerization. In the former case it is possible that the enzyme system responsible for synthesizing chondroitin sulphate or some of its components would show an increase during the healing of rickets brought about by vitamin D, just in the same manner as the citric acid content and the enzyme concerned with its formation were found to show an increase in the rachitic epiphyseal cartilage of rat and dog after vitamin D administration³. Castellani and Zambotti⁴ have recently demonstrated that the epiphyseal cartilage of growing rabbit contained appreciable amounts of a thermolabile enzyme system which synthesizes one of the components of chondroitin sulphate, namely, hexosamine from glutamine and glucose-6-phosphate. In view of these considerations, it was felt desirable to investigate whether vitamin D influenced the enzymatic synthesis of hexosamine in the rachitic cartilage.