Effects of treadmill running on glycosaminoglycans in articular cartilage of rabbits.

In a study of the effects of motion load on weight-bearing articular cartilage, rabbits were made to run on a treadmill for 1-, 5-, and 30-day periods. One group ran on a level surface, and another ran uphill. In vivo 35S-sulfate bound in glycosaminoglycans (GAG) after running was used as an indicator of the synthesis rate of GAGs. The GAG content of the tibial and femoral cartilages was measured from determinations of uronic acid, galactosamine, and glucosamine in GAGs after papain proteolysis and purification. Uphill running caused a depletion of the bound 35S-sulfate incorporated in GAGs in both tibial and femoral weight-bearing cartilage (5 days: P less than 0.001 and P less than 0.01, respectively; 30 days, tibial cartilage: P less than 0.01). The concentrations of uronic acid and galactosamine were mainly unaltered, except after 1 day of running when an increased concentration of both substances was found, particularly in rabbits running on a level surface (uronic acid: P less than 0.05; galactosamine: P less than 0.001). After 30 days of running the glucosamine content was markedly reduced in GAGs of both tibial and femoral cartilage (P less than 0.05). The possible role of different factors affecting the cartilage metabolism is discussed.