Change of joint synovial clearance speed in experimental arthritis

The radio activity of 131I-Hippuran injected into the knees was investigated in rabbits and found to decrease with passage of the time. The disappearance curve was monoexponential and the disappearance rate was able to be obtained by a biological half life (T 1/2). This evidence showed that 131I-Hippuran was absorbed from the knee and excreted into body blood circulation but was not able to return to the knee again, and might provide a suitable parameter for the joint clearance. The mean value of T 1/2 in normal 25 knees was 13.9 +/- 4.5 min. The effect of 0.1N oxalic acid on the T 1/2 was investigated in 20 knees 24 hours after intra-articular injection, in 17 knees 4 days, in 14 knees 7 days, in 11 knees 12 days and in 9 knees 20 days. The mean T 1/2 value was 50.4 +/- 9.8 min., 30.6 +/- 6.2 min., 20.9 +/- 4.4 min., 15.2 +/- 2.2 min., and 13.7 +/- 2.5 min., respectively. The significant difference was observed between the groups of 24 hours, 4 days and 7 days. Hemorrhagic arthritis was observed in the rabbit knee with oxalic acid injection. The very severe hemorrhagic change was observed in the specimen obtained 24 hours and 4 days after the injection. On the 7 days after that the arthritic condition began to heal and almost complete healing was observed on 12 to 20 days. These results indicated that the joint clearance of 131I-Hippuran was reflected well in the pathological change induced by oxalic acid. It is interpreted to mean that the inhibition of synovial blood circulation by oxalic acid might cause decrease of absorption and clearance rate of 131I-Hippuran in the knee. It is thought that the measurement of the biological half life (T 1/2) after the intra-articular injection of 131I-Hippuran is a suitable method mainly to understand the condition of absorption and excretion of the joint through the synovial blood vessels.