The amino acid hydroxyproline constitutes approximately 13 per cent of collagen (1, 2), and 1 to 2 per cent of elastin (2). It is present in no other protein of the body. For this reason, the determination of hydroxyproline has been utilized for the estimation of collagen in various animal tissues (3), and in the fibrinoid material of the subcutaneous nodule of rheumatoid arthritis (4).It is, at the present time, not clear whether in the diseases of the connective tissue, or "collagen diseases," significant alteration and degradation of the protein collagen occurs. The light microscope studies of Klinge (5) and of Bahrmann (6), who observed swelling of collagen in tissue sections of lesions from patients with rheumatic and other diseases, suggested that these changes do occur. Others (7-9) have shown in addition that swelling and focal degeneration of collagen fibers is a common and striking effect of anaphylactoid hypersensitivity reactions.Using the electron microscope, however, Gross (10) and Gale (11) did not find abnormal fibers in material from lesions of rheumatoid arthritis, rheumatic fever, disseminated lupus erythematosus, and scleroderma. Though Wolpers (12) did observe fibrils lacking cross striations in necrotic areas of old rheumatoid nodules, the fibers were normal in non-necrotic areas and in samples of collagen obtained from Arthus lesions. When cross sections of rheumatoid nodules were submitted to careful X-ray diffraction study by Kellgren, Ball, Astbury, Reed, and Beighton (13) In contrast to the preceding workers, Rich, Voisin, and Bang (14) did observe altered fibrils in a small percentage of samples of tissue from Arthus lesions examined with the electron microscope. The fibrinoid material of the subcutaneous nodule of rheumatoid arthritis has recently been extracted (4) and found to contain negligible amounts of hydroxyproline, indicating that, in all probability, it does not contain degraded collagen and arises from other components of the connective tissue.Because hydroxyproline is present almost entirely in collagen, it was felt that if there were a significant deviation from normal in the metabolism of collagen or an increase in degradation of this protein in patients with collagen diseases, these changes might be reflected by increased levels of excretion of this amino acid in urine. METHODSSixty-four patients were studied, of whom 48 were adults ranging in age from 17 to 74, and 16 were children ranging in age from 5 to 14. Twenty-four of the adults were men and 22 women; all but one of the children were boys. Among the adults, 8 were normal individuals and 16 had rheumatoid arthritis. Eight had one of the collagen diseases, i.e., 2 had disseminated scleroderma; 1, isolated scleroderma; 2, disseminated lupus erythematosus; 1, dermatomyositis; and 2, acute rheumatic fever. Sixteen had one of a group of miscellaneous diseases; these included 4 patients with resolving pneumonia, and one patient each with the following conditions: multiple sclerosis, coronary heart disease, acromegaly...

The relatively simple composition of hyaline cartilage (1, 2) offers a unique opportunity to investigate the mechanism of erosion of this tissue in the presence of inflammatory synovitis. Shatton, Schubert and Malawista (1,2) have shown that about half of the dry weight of bovine nasal cartilage consists of chondromucoprotein material. A protein preparation of similar composition has been isolated from human rib cartilage (3). The other half of dried cartilage consists mainly of collagen (2). In the absence of evidence of an enzyme that can attack native collagen at physiological pH, it appeared logical to investigate the possibility that the primary process occurring during the erosion of cartilage was the degradation of the chondromucoprotein. Accordingly, the effect of extracts of leukocytes and inflamed synovial membrane on the chondromucoprotein was studied.Chondromucoprotein as extracted by Shatton and Schubert (1) contains about 70 per cent chondroitin sulfate and 30 per cent protein. It is water-soluble and highly viscous in solution. The latter property is in contrast to that of free chondroitin sulfate, which forms solutions of relatively low viscosity. On the basis of this difference, the rate of breakdown of the mucoprotein under the influence of cell-free extracts of leukocytes from the peripheral blood and of synovial membranes from patients with a variety of arthritides has been measured. Rapid decrease in viscosity on treatment with extracts of normal leukocytes and rheumatoid synovial membranes has been observed. Leukocyte extracts. Pellets of leukocytes obtained from the peripheral blood of normal subjects and of hospitalized patients with a normal peripheral blood picture were prepared by the addition of 1 vol of 6 per cent dextran solution to 3 vol of heparinized blood distributed in 15 ml conical centrifuge tubes. After allowing them to stand for 1 hour at 370 C, the supernatants were removed and centrifuged. The pellet obtained from 60 ml of heparinized blood was taken up in 2 ml of distilled water and alternately frozen and thawed 10 times using an ice-salt bath. The mixture was then ground in a small glass homogenizer and centrifuged. The clear pink supernatant was brought to a volume of 3 ml.Synovial membrane extracts. Synovial membrane was obtained through the cooperation of Dr. R. L. Preston from patients with rheumatoid arthritis, ankylosing spondylitis, and osteoarthritis of the hip and knee, who were undergoing joint surgery. The fresh synovial tissue was minced with scissors in the cold. Approximately 2.5 g of minced tissue was homogenized in 2.5 ml of water using a glass homogenizer. The homogenate was then alternately frozen and thawed 10 times using an ice-salt mixture and cleared by centrifugation.Viscosity measurements. Four ml of a 0.5 per cent solution of the chondromucoprotein in neutral salinephosphate buffer (0.075 M sodium chloride and 0.075 M phosphate) was pipetted into a 4 ml Ostwald viscosimeter placed in a water bath at 37°C. Following a period of 15 minutes for tem...