Dibutyryl cyclic AMP decreases expression of ED-A fibronectin by canine chondrocytes.

The presence of Extra Domain A (ED-A) in fibronectins from cartilage and from the culture medium of chondrocytes cultured under various conditions was determined with monoclonal antibody IST-9. Less than 2% of the fibronectin extracted from cartilage was fibronectin which contained the ED-A sequence (ED-A fibronectin). Chondrocytes placed in primary culture began to synthesize increased amounts of ED-A fibronectin (6% to 36% of the total fibronectin). Expression of ED-A fibronectin was selectively reduced when the chondrocytes were cultured in the presence of 0.5 mM dibutyryl cyclic AMP.