The effects of anti-inflammatory drugs upon the chemistry and enzymology of rat skin

Abstract

Normal rats contain in the extracellular extrafibrillar compartment of their skin no proteolytic or “free” collagenolytic activities. Within 26 hr after administration of Cortisol, prednisolone, indomethacin, or oxyphenylbutazone, this cutaneous compartment demonstrated both a proteolytic and a free collagenolytic activity. Salicylate administration to rats did not produce these results. Associated with the appearance of these two enzymatic activities in the extracellular compartment of the skin were supernormal amounts of RNA and normal or subnormal amounts of β-glucuronidase activity. For these and other reasons it was felt that neither the proteolytic activity (maximal at pH 7.5) nor the collagneolytic activity (maximal at pH 5.5) was derived from the breakdown of intracellular lysosomes. Finally, paralleling the appearance of cutaneous, extracellular, free, collagenolytic activity was the loss of as much as 25–30 per cent of the insoluble collagen from the skin of these drug-treated rats. The extracellular, cutaneous proteolytic activity described above could digest hemoglobin and fibrin clots at pH 7.5 and convert fibrinogen to fibrin at the same pH. This enzyme activity could not attack the synthetic substrate appropriate to trypsin or thrombin but was active upon the substrate for chymotrypsin. Both the proteolytic and clotting activities were inhibited equally by p-chloromercurobeozoate, salicylate, and soybean trypsin inhibitor. Therefore this clotting activity was not due to thrombin but represents a hitherto unknown clotting activity found only in the skin of drugtreated rats. The free collagenolytic activity found extracellularly in the skin of drug-treated rats had properties identical with those demonstrated by trypsin-activated extracts from normal rat skin. Apparently this collagenolytic activity is also released from cells by drug administration into the extracellular compartment of the skin where it effects the enzymatic digestion of cutaneous collagen until it complexes with an inhibitor pre-existing in this compartment.