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. 2011:2011:494168.
doi: 10.1155/2011/494168. Epub 2011 Apr 28.

Mechanisms of phosphine toxicity

Nisa S Nath  1 , Ishita Bhattacharya, Andrew G Tuck, David I Schlipalius, Paul R Ebert
Affiliations

Mechanisms of phosphine toxicity

Nisa S Nath et al. J Toxicol. 2011.

Abstract

Fumigation with phosphine gas is by far the most widely used treatment for the protection of stored grain against insect pests. The development of high-level resistance in insects now threatens its continued use. As there is no suitable chemical to replace phosphine, it is essential to understand the mechanisms of phosphine toxicity to increase the effectiveness of resistance management. Because phosphine is such a simple molecule (PH(3)), the chemistry of phosphorus is central to its toxicity. The elements above and below phosphorus in the periodic table are nitrogen (N) and arsenic (As), which also produce toxic hydrides, namely, NH(3) and AsH(3). The three hydrides cause related symptoms and similar changes to cellular and organismal physiology, including disruption of the sympathetic nervous system, suppressed energy metabolism and toxic changes to the redox state of the cell. We propose that these three effects are interdependent contributors to phosphine toxicity.

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Figures

Figure 1
Figure 1
Interaction of phosphine with enzymes involved in metabolic processes and acetylcholine signalling. Sites of interaction with arsenite and nitric oxide (NO) are also shown: phosphine (green), arsenite (dark blue), and nitric oxide (light blue). Sites of ROS generation (red) are indicated as well. The cross behind the names of targeted enzymes indicates that they are inhibited. The potassium and calcium currents are regulated by acetylcholine via NO. Ca2+ triggers the release of acetylcholine from vesicles in the cytoplasm into the neuronal synapse. The acetylcholinesterase degrades acetylcholine, which reduces the strength of neurotransmission. The net effect is that arsenite and phosphine increase acetylcholine signalling by inhibiting the esterase. FAD/FADH2 (Flavin adenine dinucleotide oxidised/reduced), NAD+/NADH (nicotinamide adenine dinucleotide oxidised/reduced), ADP/ATP (adenosine di/tri nucleotide), NO (nitric oxide), ROS (reactive oxygen species), and TCA (tricarboxylic acid).
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