AUTORADIOGRAPHIC VISUALIZATION OF THE ENTRY AND TRANSIT OF S35 IN CARTILAGE, BONE, AND DENTINE OF YOUNG RATS AND THE EFFECT OF HYALURONIDASE IN VITRO

Abstract

The fate of radiosulphate introduced in young suckling rats has been followed by autoradiography of formalin–ethanol fixed celloidin sections. In the cartilaginous epiphyses of long bones, the radioelement has been detected first in the cells, particularly at the hypertrophic level, then in cells and matrix, and finally in matrix exclusively. The incorporated radiosulphate was later displaced towards the ossification area by the growth process. During this migration, the relative intensity of the autoradiograph decreased progressively. This series of events was interpreted as visualization of chondroitin sulphate synthesis, secretion, and utilization or turnover. The S³⁵ labelled substance was rapidly hydrolyzed by hyaluronidase except in areas of tendon insertions. In bone and dentine, an over-all initial exchange picture was replaced by a growth line of acid fast, hyaluronidase labile, sulphated material which became displaced along with bone salts by further growth. This material was metachromatic with toluidine blue. It is thought to be also chondroitin sulphate and its possible relationship to mineralization has been discussed.