Rhodnius prolixus: effects of the neolignan burchellin on in vivo and in vitro diuresis

Supplementation of blood with the neolignan burchellin (100 mu g/ml), a com pound from the arboreous Lauraceae Aniba burchelli, affected the course of excretion of fourth-instar larvae of Rhodnius prolixus, especially directly after feeding, and reduced the volume of feces/urine excreted within 6 h o f feeding to about 18% and, on the simultaneous addition of the diuretic ho rmone analogue 5-hydroxytryptamine (5-HT), about 71% of that observed in un treated bugs. In the latter, 5-HT induced a significant 60% increase in exc retion. Regardless of whether Malpighian tubules originating from unfed, un treated or fed, burchellin-treated bugs were incubated in vitro in the hemo lymph of these bugs or in physiological saline supplemented with 5-HT with or without burchellin or in homogenates of thoracic ganglionic masses of un treated and treated bugs, burchellin was consistently found to affect the s ecretion rates. Therefore, burchellin not only depresses the release of the diuretic hormone or induces the release of antidiuretic factors but also d irectly affects the Malpighian tubules.