THE TOXIC ACTION OF PREPARATIONS CONTAINING THE OXYGEN-LABILE HEMOLYSIN OF STREPTOCOCCUS PYOGENES

IV. COMPARISON OF CARDIOTOXIC ACTION WITH THAT OF SAPONIN

¹ From the Department of Pharmacology, Long Island College of Medicine, Brooklyn, New York and the Department of Bacteriology, New York University College of Medicine, New York, New York

1. The cardiotoxic action of saponin has been compared with that of preparations containing the oxygen-labile hemolysin of streptococci.

2. Exposure of the heart to a single application of the streptococcal preparation (SPA) increases the responsiveness of the heart to saponin. Conversely, exposure of a heart to a subcontracturing dose of saponin increases its responsiveness to SPA.

3. Exposure of the heart to a mixture of the two agents produces an effect, systolic contracture, which is not elicited by either agent acting alone in the same concentration.

4. Exposure of the heart to a single application of SPA sensitizes the heart to a second application of SPA. Exposure of a heart to a comparable concentration of saponin fails to sensitize to a second application of saponin.

5. The hemolytic actions of SPA and saponin are not additive.

6. Release of an inhibitor accompanies the first exposure of a heart to SPA, but does not accompany exposure of a heart to saponin in any of the concentrations tested.

7. Inhibitor-fluid prevents the contracturing action of SPA, but prevents neither the contracturing action of saponin nor the sensitizing action of SPA.

8. It is postulated that the ultimate site of action of the cardiotoxic agents is normally covered by two barriers, one of which can be displaced by saponin, the other by SPA, and that exposure of the ultimate site of action must occur before either agent can produce systolic contracture.