Fibrin clot retraction by human skin fibroblasts: effects of ADP and thrombin.

Thrombin stimulated human skin fibroblasts to retract fibrin clots. When Bothrops marajoensis thrombinlike enzyme was substituted for thrombin, no retraction occurred. Fibroblasts were found to contain 12 nmole of ATP and 3.6 nmole of ADP/mg of protein, a value closely resembling that of nonmetabolic adenine nucleotides in platelets. Thrombin caused neither release of adenine nucleotides from the suspension of fibroblasts harvested enzymatically nor did addition of ADP stimulate fibroblasts to retract fibrin clots.