Connective tissue activation by synovial fluids and synovial-tissue extracts of rheumatoid arthritis patients

Decreased NA+, K+-ATPase activity in erythrocyte membrane from rheumatoid arthritis patients

The activity of the plasma membrane Na+/K+-ATPase and cellular sodium (Nai) and potassium (Ki) content were analysed in RBCs from 15 rheumatoid arthritis (RA) and 30 reference subjects (11 healthy controls, 12 osteoarthritis and 7 gouty patients). Na+/K+-ATPase activity was determined by measuring the inorganic phosphate (Pi) released by incubation in a reaction medium in the presence and absence of K ions or ouabain. Nai and Ki were measured with an ion-selective electrode analyser on the hemolysates, after washing the RBCs in 110 mM MgCl2. The Na/K-ATPase activity was significantly lower in RA patients than in both healthy controls and patients with osteoarthritis or gout. A slight but significant increase in Nai was observed in rheumatoid subjects. It is hypothesized that the decrease in the Na+/K+-ATPase activity in RA may be the result of a defective expression of membrane proteins, which is probably related to the altered cell sensitivity observed.

Dependence of collagen synthesis by embryonic chick tendon cells on the extracellular concentrations of glutamine

An agent in rheumatoid synovial fluid which stimulates collagen synthesis by embryonic chick tendon cells was identified as glutamine. The stimulating effect was observed only at a subnormal concentration of proline (0.02 mM). The concentration of glutamine in rheumatoid synovial fluid is about 2.5 mM but it falls rapidly during storage even at -20 degrees C. Collagen synthesis is shown to depend on the extracellular concentrations of glutamine and proline in addition to any connective tissue activating factors.

Connective tissue activation by synovial fluids and synovial-tissue extracts of rheumatoid arthritis patients

Prompted by Castor's investigations (4) on a connective-tissue-activating peptide (CTAP) we investigated the stimulative effect of synovial fluids and synovial-tissue extracts on the synthesis of collagen by incubated embryonic-chick tendon cells. The stimulative effect was greater with synovial-tissue extracts from more severe cases than with samples from patients having milder forms of the disease. There was no correlation between the stimulation by synovial fluids and synovial-tissue extracts from the same patient. The stimulative activity was lost at dialysis. A slight stimulation in the incorporation of glucosamine was also observed. Treatment of the patients with gold, chloroquine or steroids decreased the stimulating capacity. These effects seem to depend on factors different from those described by Castor. The differerences in the stimulant activity of samples from various groups cannot be entirely due to glutamine, which is one of the limiting nutrients of the embryonic-chick tendon cells.