Abstract
Hyaline cartilage was obtained from patients undergoing synovectomy of the knee joint for rheumatoid arthritis. Eroded cartilage from beneath the invading pannus and relatively normal cartilage from the same joint were maintained in organ culture for three days. During the first 48 hours in culture the explants were exposed to 35SO4 in the medium. The equivalent layers of normal and eroded cartilage were analysed for DNA uronic acid and 35SO4 incorporation. There was a decrease in the DNA and uronic acid of the eroded cartilage, although only the latter reached statistical significance. The uptake of radioactive sulphate was significantly greater in explants taken from the eroded site than from normal areas. This increase in metabolic activity could well be a protective phenomenon.