Diamphidia toxin, the bushmen's arrow poison: possible mechanism of prey-killing.

The effects of a 60,000 mol. wt protein from the pupae of the beetle, Diamphidia nigro-ornata have been studied. In concentrations as high as 50 micrograms/ml, the toxin has little effect on the propagated compound action potential of isolated nerve trunks, or on the voltage-gated sodium and potassium channels of voltage-clamped single skeletal muscle fibers. In the anesthetized cat, the toxin has no specific effect on the neuro-muscular or the cardiovascular systems. It has a markedly hemolytic effect, and could reduce hemoglobin levels by as much as 75%. Plasma hemoglobin is increased, with resultant extensive hemoglobinuria and associated histopathological changes in the kidneys. Blood pressure, heart rate, PO2, PCO2, and oxygen-saturation remain essentially normal until the terminal stages of intoxication. Contrary to previous conclusions, we find no support for any particular neurotoxicity of the poison. The complex systemic effects, and possibly the prey-killing, can probably be attributed to the extensive hemolysis, reduced oxygen-carrying capacity, and generalized tissue hypoxia.

The Bushman arrow toxin, Diamphidia toxin: isolation from pupae of Diamphidia nigro-ornata.

The Bushmen of the Kalahari Desert in Botswana use the pupae of the beetle Diamphidia nigro-ornata Ståhl to poison their arrows. Sequential aqueous extraction, ammonium sulfate precipitation, ultrafiltration and chromatofocusing have given an apparently homogeneous active protein from these pupae with an approximate mol. wt of 54,000, an isoelectric point of about 8.0 pH and a lethal potency (minimum lethal dose, MLD) between 5 and 20 micrograms/kg (i.p. mouse). Preliminary pharmacological studies on less purified material show that, after a delay, this Diamphidia toxin causes sustained contraction of isolated intestinal smooth muscle. This contraction is not blocked by atropine or mepyramine and, therefore, is not due to release of acetylcholine or histamine. Results on the phrenic nerve - hemidiaphragm preparation demonstrate that in the presence of the toxin, contraction in response to indirect stimulation gradually fails and is accompanied by contracture. Since direct stimulation of the muscle still elicits a contraction, the toxin apparently does not affect the contractile mechanism itself. We conclude that Diamphidia pupae contain a protein toxin that is responsible for its lethality. Although this toxin appears to differ in some properties from the toxins reported by Mebs et al., de la Harpe et al. and Kündig, these protein preparations undoubtedly correspond to each other. We did not find any evidence of the low molecular weight toxic component reported by Mebs et al.