[Distribution of intravenously injected enzymes of heterologous, homologous and autologous origin. Distribution and transport of cell enzymes within the extracellular space. III (author's transl)].

The disappearance rates of intravenously injected enzymes of heterologous, homologous and autologous origin were determined in rats. Within four hours after administration, the activities show an exponential decline, that is either mono- or biphasic. The constant of the exponential function is a measure of the capillary permeability. In the case of biphasic disappearance this holds true only for the first slope, whereas the second one represents the elimination of active enzyme molecules from the extracellular space. If the decline in enzyme activity is monophasic the elimination of those enzymes from the interstitial space is limited by the permeability of the capillary membrane. Enzymes of homologous and autologous origin (extracts of liver or muscle) show a close correlation between their molecular weights and their rates of distribution within the extracellular compartment. For heterologous enzymes (crystallized) such a correlation could not be found. Possible causes for these differences in distribution are discussed. Heterologous and/or crystallized enzymes seem not to be suited for studies on the distribution of cell enzymes within the extracellular space. After enzymes are released from injured cells they undergo the processes of distribution, transport and elimination which are superimposed. The effects of the distribution and transport of enzymes on the results of clinical studies on enzyme elimination are discussed. It seems questionable at this point to assume that from the elimination rate of enzymes and their actual plasma activity one can account for the amount of enzymes originally released from injured cells.