2,4-D metabolism

Huang [69], the ether bond in 2,4-D is cleaved to produce 2,4-didblorophenol by a 2,4-D monooxygenase [148]. The hydixn lation of 2,4-dichlorophenol to form 3,5-dichlorocatechol has now been well established [149,150]. In the author s laboratory, Radjendirane et al. [151] and Bhat et al. [162] studied the second and third enzymes of the 2,4-D metabolic pathway in Pseudomonas cepacia strain CSV90, respectively. Both the... 

Leguay JJ, Guern J (1977) Quantitative effects of 2,4-dichlorophenoxyacetic acid on growth of suspension-cultured Acer pseudoplatanus cells. II. Influence of 2,4-D metabolism and intracellular pH on the control of cell division by intracellular 2,4-D concentration. Plant Physiol 60 265-270... 

The fundamental chemistry, especially of the newer economic poisons, is of primary importance. The mechanism of action of the various types of economic poisons and the relation of structure to toxicity of insects are of fundamental interest. Chemical versus biological methods of evaluation should be presented. Performance methods of evaluation of these chemicals have been given careful consideration by several workers. Emphasis was placed by several workers on the need for much additional information on various aspects of the problem regarding the use of DDT, 2,4-D, and other pesticides. There is direct importance in studies on the metabolism of DDT. 

Rawlings, N.C., S.J. Cook, and D. Waldbillig. 1998. Effects of the pesticides carbofuran, chlorpyrifos, dimethoate, lindane, triallate, trifluralin, 2,4-D, and pentachlorophenol on the metabolic endocrine and reproductive endocrine system in ewes. Jour. Toxicol. Environ. Health 54A 21-36. 

Some further generalities can be made from data in this table. Except for octane with its known CNS depressant actions, no other compound appeared in significant quantities in the brain. The herbicides were the only compounds which occurred in significant concentrations in the bile and this has been shown (32) to be mainly metabolites, i.e., the taurine conjugates of 2,4-D and 2,4,5-T. Also the kidney and urine samples contained large concentrations of these same herbicides as did those from fish treated with octane or DEHP. Presumably these latter values are at least in part metabolities. Due to its large mass (ca. 

Faulkner, J.K. and Woodstock, D. Metabolism of 2,4-dichlorophenoxyacetic acid (2,4-D) by AspergUlus nlger. Nature (London), 203 865, 1964. 

Chaturvedi (1993) also examined the effect of mixtures of 10 pesticides (alachlor, aldrin, atrazine, 2,4-D, DDT, dieldrin, endosulfan, lindane, parathion, and toxaphene) administered by oral intubations or by drinking water on the xenobiotic-metabolizing enzymes in male mice. He concluded, The pesticide mixtures have the capability to induce the xenobiotic-metabolizing enzymes, which possibly would not have been observed with individual pesticides at the doses and experimental conditions used in the study. ... 

The lowest dose effects of diuron are seen at 0.27 mg kg-1 per day. Almost all of the low-dose expression changes are related to genes involved with xenobiotic metabolism and transport, including cytochrome P450 enzymes and several transferases. These data indicate that the cells are responding appropriately to a potentially toxic xenobiotic. These effects are widespread across the set of chemicals tested in ToxCast, so it is of interest that 2,4-D does not trigger a similar xenobiotic metabolism response. 

Dichlorophenol may be released to the environment in effluents from its manufacture and use as a chemical intermediate and from chlorination processes involving water treatment and wood-pulp bleaching. Releases can also occur from various incineration processes, from metabolism of various pesticides in soil or in the use of 2,4-D, in which it is an impurity. It has been detected at low levels in drinking-water, groundwater and ambient water samples (United States National Library of Medicine, 1997). 

However, active uptake mechanisms have now been found in some bacteria for various xenobiotic organic anions. These include 4-chlorobenzoate (Groenewegen et al., 1990), 4-toluene sulfonate (Locher et al., 1993), 2,4-D (Leveau et al., 1998), mecoprop and dichlorprop (Zipper et al., 1998), and even aminopolycarboxylates (Egli, 2001). Such active uptake appears to be driven by the proton motive force (i.e., accumulation of protons in bacterial cytoplasm). These transport mechanisms exhibit saturation kinetics (e.g., Zipper et al., 1998), and so their quantitative treatment is the same as other enzyme-limited metabolic processes (discussed below as Michaelis-Menten cases). 

T urinary excretion by rats, but much slower excretion in dogs with some metabolism occurring. Excretion occurred by first order processes with half elimination values (E /2) f°r man, rats, and dogs of 23, 14, and 87 h, respectively. In man, Sauerhoff et al. (20 found Ej/2 values of 18 h for 2,4-D. Kohli et al.(5,6) and Sauerhoff jet aJL. (2) found Ej/2 plasma values of 33, 19 and 12 h for 2,4-D, 2,4,5-T, 2,4-D respectively. Sauerhoff et al. ( 7) observed that urinary excretion was even more rapid (E /2 ... 

The authors thank the 43 volunteer 2,4-D applicators who participated in this study North Dakota State University Extension personnel and the Washington State Chapter of National Agricultural Aviation Association who contacted the participants W. C. Aller, Yakima Laboratory for collection of urine samples from Eastern Washington and assistance in the analysis of these samples and D. S. Frear, Plant Metabolism Laboratory, USDA, SEA-AR, Fargo, North Dakota. 

Figure 8.4. Photographs of Daucus carota cell suspensions treated with hormones. 2,4-Dichlo-rophenoxyacetic acid (2,4-D) 6-benzylaminopurine (6BAP). (A, control B, control + 2,4-D + 6BAP C, control + 2,4-D D, control + 6BAP). Reprinted from Muscolo, A., Bovalo, F., Gionfriddo, F., and Nardi, S. (1999). Earthworm humic matter produces auxin-like effects on Daucus carota cell growth and nitrate metabolism. Soil Biol. Biochem. 31,1303-1311, with permission from Elsevier Limited.

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