Collagenase is believed to be important for cell migration and collagen remodeling during tissue repair and regeneration. We have investigated collagenase concentrations in different types of surgically inflicted wounds in pigs. Collagenase was extracted from tissue homogenates of wounds by heating to 60 degrees C for 6 min in 0.1 M CaCl2. The molecular weight of latent collagenase was about 52 kDa. Activated collagenase produced the characteristic 3/4 fragment of collagen. Collagenase was assayed by the use of radiolabeled telopeptide-free collagen. To detect maximal collagenase activity, extracts were reduced and alkylated to destroy inhibitors, then activated with aminophenylmercuric acetate. Sutured incisions showed peak collagenase content on postoperative day 1 and thereafter steadily declining concentrations. Granulation tissue from non-sutured large defect full-thickness wounds showed high collagenase content on postoperative day 5 and then a sharp decline to day 7 followed by a slowly declining curve to postoperative day 21. Partial-thickness wounds exhibited a different time course, with collagenase increasing to peak concentrations on postoperative days 3-5; however, a large proportion of the detected collagenase was due to the adherent scab. By day 7 collagenase concentrations approached the low concentrations of normal skin when epithelialization was complete and the scab rejected. In general, collagenase shows an early maximum and then declines with postoperative time, with the sharpest decline occurring when epithelialization is complete.