Antibody Concentration and Temperature as Determinants of In Vitro Sensitization and Histamine Release in Isolated Cardiac Tissues

Abstract

The process of cardiac anaphylaxis was studied on the isolated hearts and separate cardiac tissues obtained from actively and passively sensitized guinea pigs, as well as on tissues obtained from normal animals and sensitized in vitro with rabbit antiovalbumin. The results of studies made on whole hearts and the individual tissues confirm that the histaminase activity of the organ is negligible, that the atria, which comprise only 12% of the mass of the heart, account for 50% of the histamine release of the whole organ, and that the histamine content of the right atrium is 44% greater than that of the left. The degree and velocity of in vitro sensitization was shown to be influenced by antibody concentration, the proportion of specific to nonspecific γ-globulin molecules and by temperature, even though the overall magnitude of physical binding of antibody proved to be temperature independent. At a constant degree of sensitization, histamine release depends on the concentration of antigen used for challenge. The anaphylactic release of histamine from both actively and passively sensitized atria takes place in the temperature range 24° to 44°C and has a maximum at 40°C. Following challenge, atrial histamine release reaches a maximum at 1.5 min, with a velocity dependent on the temperature. From the variation of initial velocity with temperature in tissues having a constant degree of sensitization, it was possible to show the activation energy of histamine release to be 23 kcal.