Study of Dieffenbachia-induced edema in mouse and rat hindpaw: Respective role of oxalate needles and trypsin-like protease

The stem juice of Dieffenbachia plants produces prominent edema when injected into the paws of mice and rats. To determine the components responsible for this activity, we prepared and injected different preparations of stem juice and measured the degree of edema they induced. In mice treated with crude Dieffenbachia stem juice, swelling of the paw reached a peak within 4 hr after injection when the weight of paws treated with 40 μl of crude juice was approximately doubled. After centrifugation of crude juice the insoluble fraction, containing numerous calcium oxalate crystals, induced a similar swelling. The soluble fraction showed a trypsin-like proteolytic activity but led to only a slight edema (35% weight increase with 40 μl of preparation). A suspension of oxalate needles (0.1 g% which was the same concentration as in crude juice), isolated from plant stems, caused minimal edema (10% weight increase) which was not further increased by the presence of the proteolytic fraction. We concluded that the oxalate needles and the protease were not the principal phlogogenic substances of Dieffenbachia. In the rat, the pharmacological characterization of the paw edema was approached by oral pretreatment with cyproheptadine (10 mg/kg) or indomethacin (2.5,5, and 10 mg/kg). Our results suggested that histamine and/or serotonin played a role in the early response, and prostaglandins in the plateau phase (3–4 hr after injection of the crude juice). The soluble fraction of stem juice hydrolyzed the synthetic substrate N-benzoyl-dl-arginine-para-nitroenilide) specific for trypsin-like hydrolytic activity, but did not release bradykinin-like substance from plasma in vitro. In vitro bradykinin-like release was obtained with a purified fraction of Dieffenbachia stem juice that had specific proteolytic activity five-fold higher than crude juice. Our results explain the origin of the slight edema due to the soluble fraction of stem juice. However additional studies are required to define the role played by the protease in Dieffenbachia intoxication.