ON THE CHEMICAL PATHOLOGY OF INTERSTITIAL FLUID. I. PROTEOLYTIC ACTIVITIES IN TRANSPLANTED MOUSE TUMORS.

Abstract

Enzymatic assays on cell- and blood-free interstitial fluid from central tumor regions of 3 transplanted mice tumors and 1 rat tumor are presented. The fluid was sampled in microquantities by a direct capillary technic under close visual control. Comparison was made with the corresponding activities of normal plasma and intraperitoneal fluid. All activities have been expressed on a per microliter basis. The main purpose was to characterize the different enzyme activities hydrolyzing carbamide bonds by using a variety of conventional substrates and to study the different activity levels as they appear in native samples of interstitial tumor fluid. Tumor fluids contained, in general, markedly increased activities of acid proteinases, mainly cathepsin D and to some extent cathepsin B , and very high levels of polypeptidase, aminopeptidase, and dipeptidase activities. Tumor fluids had some cathepsin C activity, but very low neutral proteinase activity. No OH-dependent proteinase activity was observed. The only carbamide bond-splitting enzymes which showed reduced activity in tumor fluids, probably due to inhibition, were cathepsin B between pH 6–8, as measured against N -benzoyl-dl-arginine-naphthylamide (BANA), and carboxypeptidases. The activity of the heterogeneous group of l-leucyl-β-naphthylamide (LNA) splitting enzymes was markedly increased in all tumor fluids. It is concluded that the enzymatic composition of tumor interstitial fluid is strongly shifted to favor the hydrolysis of polypeptides and most types of smaller l-forms of peptides and amides.