Examination of the pathogenesis of
shock has directed attention to the microcirculation, the kidneys, and the lungs. Today, apart from other tissues and organs, particularly the splanchnic organs, the pancreas is also incriminated. The lysosomes (also present in other tissues) and zymogen granules it contains are responsible, during the ischaemia and
hypoxia typical of
shock, for the instigation of a process of cell
autolysis that releases
enzymes and frequently toxic
protein fragments into the bloodstream. These include
myocardial depressant factor (
MDF), whose physical, chemical and
biological identification and rôle are now fairly clear. First described by Brand & Lefer in 1966,
MDF has been explored by Lefer and other workers at both the experimental and clinical level. An account is given of the main researches that have led to the determination of the characteristics and action of
MDF in numerous types of
shock, the pattern of its formation, and the routes by which it is introduced into the circulation. Reference is made to work showing the close relation between
MDF and the lysosomial
hydrolases, and its
biological effects on the whole animal, on isolated preparations, and in vitro. In addition to the
myocardial depressant effect that has given it its name,
MDF has been shown to provoke ischaemia of the splanchnic circulation and depression of the RES. The evidence on both sides is presented, including that derived from personal investigations of district haemodynamics in experimental
shock. In substance, material is presented from which an objective approach can be taken to the cultural contribution of
MDF in the matter of
shock, its prospects, and its limitations.