Autolysis

Autolysis (from the Greek autos - self and lysis - dissolution, destruction), the process of breakdown of tissues and cells of an organism, preserved after its death under sterile conditions, due to the action of enzymes contained in these tissues. The phenomena of A. were first described by Salkowski, who observed it in sterile samples and preserved tissues of the liver, muscles, and adrenal glands. Since the organs of animals consist mainly of proteins, the process of A. occurs, mainly, under the influence of proteolytic enzymes. The process of A. is quantitatively measured as follows: the amount of residual nitrogen is determined, i.e., the nitrogen of compounds remaining after the precipitation of proteins and representing products of their breakdown, in a portion of an organ taken immediately after death under sterile conditions; then the same measurement is performed after certain time intervals on other parts of the same organ, with the organ being preserved under sterile conditions to exclude the influence of microorganisms. The increase in residual nitrogen, expressed as a percentage relative to the initial amount, indicates the rate of the autolytic process, which to a large extent depends on the conditions in which A. occurs. With respect to temperature, the most favorable is 37°C; at lower temperatures A. proceeds much more slowly; higher temperatures also have a slowing effect; temperatures above 65-70° completely stop the process. As for the reaction of the tissues, the process proceeds most rapidly with a weakly acidic reaction, regardless of whether it is caused by the presence of mineral or organic acids. This is also related to the circumstance that A. of organs usually occurs only after a certain latent period of 2-4 hours, i.e., when the postmortem accumulation of acids is sufficient to have an accelerating effect on the course of the process. An alkaline reaction strongly slows down the course of A., which also depends on the salts and a number of other substances present in the tissues. Thus, arsenic acid has an accelerating effect on the course of A., the presence of phosphates has a slowing effect. Laquer, by saturating the tissue with oxygen, slowed down the course of the process; while the action of carbon dioxide resulted in acceleration. For different organs, the rate of autolysis is also not the same. For example, in the spleen, protein breakdown can be detected as early as 2 hours after death; in the liver - after 4 hours, in muscle-connective tissue - only after 5-6 hours. After 24 hours, the amount of residual nitrogen increases in the spleen, preserved at room temperature, by 28.8%, in the liver - by 12.6%, in muscle tissue - only by 10.0%. Autolytic processes proceed very rapidly in the tissues of malignant neoplasms, the more acidic reaction of which favorably affects the process. The products obtained from the breakdown of tissues due to A. are, in general, the same as in the breakdown of proteins in the gastrointestinal tract. The only difference is that in A. we have the action not only of proteolytic enzymes, but to a small extent also of a number of other enzymes causing deamination, oxidation and reduction processes, as well as synthetic ones. The question of whether processes of A. of tissues and cells can occur in a living organism under normal physiological conditions is still unresolved, but in all kinds of pathological processes, the phenomena of A undoubtedly play a significant role. Such is, without doubt, the breakdown of liver tissue in acute phosphorus poisoning or in yellow atrophy of the liver, in which the urine contains products of protein breakdown caused by enzymes. Similarly, without doubt, the melting of exudates in pneumonia under the influence of enzymes of leukocytes present in these exudates is also an autolytic process. The latter example is at the same time also an example of heterolysis, i.e., the process of tissue breakdown not under the influence of its own enzymes contained in this tissue, but under the influence of enzymes coming from outside. The phenomena of autolysis of organs can also be observed when, due to circulatory disorders, some parts of organs are insufficiently nourished. The damaged parts gradually break down and are absorbed, while the enzymes have no effect on the undamaged part. This circumstance is probably explained by the difference in reactions in the damaged (usually more acidic) and undamaged part of the organ.