Sauropus androgynus and papaverine do not induce bronchiolitis obliterans in Sprague-Dawley rats

In August 1995, an outbreak of bronchiolitis obliterans was observed in Taiwan. This progressive respiratory distress disease was associated with consumption of the uncooked vegetable, Sauropus androgynus. The vegetable is reportedly high in papaverine, a chemical that affects vasodilatation. This study determined whether S androgynus and papaverine induce bronchiolitis obliterans in Sprague-Dawley (S/D) rats.

The feeding doses were derived from the mean amount (in mg/kg body weight) that humans had eaten. In part A of the experiment, 30 S/D rats were fed various concentrations of S androgynus juice for eight weeks. The rats were divided into six groups, including a normal control and study groups with one time (1X), 10 times (10X, leaf only and mixed leaf and stalk) and 30 times (30X, leaf only and mixed leaf and stalk) concentration. In part B, 33 S/D rats were fed different doses of papaverine for 4 weeks. The rats were also divided into six groups, including normal control, oral feeding subgroups (1X, 10X and 20X) and intraperitoneal injection subgroups (5X and 10X). The degree of inflammation was defined semiquantitatively in the bronchioles and pulmonary vessel adventitia as including grade 0 (no inflammation), grade 1 (minimal), grade 2 (mild), grade 3 (moderate) and grade 4 (severe).

There was no evidence of bronchiolitis obliterans in either experiment. The histopathologic findings of the lungs revealed normal or only minimal inflammatory changes in the peribronchial and perivascular adventitia in each group of both studies. The mean degree of inflammatory changes in the study groups was no different from that of control group.

We conclude that ingestion of high-dose S anggogynus and papaverine do not induce injuries to the airways, alveoli or pulmonary vessels in the animal model of S/D rats. The species barrier may be one of the possible reasons.