Cis-Chlordane

Chlordane produced before 1951 contained a significant quantity of hexachlorocyclopentadiene — a toxic irritant to warm-blooded animals. Chlordane produced since 1951 contains little or none of this compound (Ingle 1965). A high-purity chlordane formulation containing about 74% cis-chlordane and 24% fims-chlordane is also available (Nomeir and Hajjar 1987). 

Technical chlordane is stable under ultraviolet (UV) light, although some components, such as chlordene, heptachlor, cis-chlordane, and /ram-chlordanc, will form photoisomers under high-intensity UV light in the presence of sensitizers, such as ketones (NRCC 1975 Menzie 1978). Several compounds were measured in alfalfa grown on soils treated with chlordane, including 1,2-... 

To study the absorption of cis-chlordane by bluegill and Xenopus, the exposure was made to 5 ppb of insecticide. The biomass and volume was one 5-g fish/6L and three 27-g Xenopus/8L in 10-liter glass cylinders. The aeration of the water was kept to the minimum and the containers were covered with aluminum foil to reduce loss due to volatilization. The radioactivity in control water without animals and in water with fish was monitored by counting 5 ml of water in 15 ml of Instagel (Packard Instruments) (16). 

Whether the isomers of chlordane, namely cis-chlordane and photo-cis-chlordane, were absorbed, retained, metabolized and excreted at similar or different rates was investigated by exposing goldfish or bluegill to 5 ppb concentration of each insecticide. 

For metabolism studies larger fish were used. Three cichlids (Cichlasoma sp.) weighing about 300g each were exposed individually in 16L of a 5 ppb solution of C-cis-chlordane. After exposure for 72 hours they were analyzed for radioactivity (18). 

In another similar experiment the treated fish were transferred to insecticide-free water to study the elimination of the absorbed cis-chlordane. Bluegill, as mentioned in the section on elimination, were also analyzed for radioactivity. Goldfish injected with l C-heptachlor (38 yg/44g fish) (19) as well as those exposed to 26 ppb l C-cis-chlordane for 24 hr (9 x 16-g fish)(20) were held in insecticide-free water for 10 days and then analyzed for radioactivity. 

Table 1. Bioaccumulation of cis-chlordane and photo-cis-chlordane by goldfish, bluegill and the amphibian Xenopus following their exposure to 5 ppb concentration in a static system.

Figure 2. Absorption of cyclodienes by fish and Xenopus in a static system (A), goldfish treated with photo-cis-chlordane (B), goldfish with cis-chlordane (C), blue gills with photodieldrin (D), blue gills with photo-cis-chlordane (E), bluegills with cis-chlorane and (F), Xenopus with ds-chlordane. All exposures were made at 5 ppb. (see Table 1 for biomass and volume of water).

Transfer of the aquatic animals, after absorption of the cyclodiene, to insecticide-free water showed variations in elimination pattern related with the chemical as well as its concentration in the body. It follows a somewhat biphasic response, there is initial rapid elimination of high concentration followed by a slow elimination at lower body concentrations (Fig. 3)(21,22, 23). Xenopus, even at low body levels of cis-chlordane, eliminate it at slightly faster rate than fish. Photo-cis-chlordane seems to be eliminated at a faster rate than cis-chlordane by both goldfish and bluegill (Table 2). The elimination of photo-cis-chlordane by goldfish and bluegill and of photodieldrin by blue-gill shows a biphasic response (Fig. 3). 

The radioactivity recovered from water showed the presence of unchanged cis-chlordane in the organic phase along with several hydrophilic metabolites (Fig. 4). Most of the radioactivity in both organic and aqueous phases was in the form of conjugates. 

Figure 4. TLC behavior (0.25 mm, Silica gel GF-254 hexane-ethyl acetate, 9 1) of organic extracts of t4C-cis-chlordane treated cichlids (A) and exposure water (C). Fractions B and D show the compounds released by acid hydrolysis of aqueous phase of fish homogenate and exposure water, respectively.

The analyses involved the exposure of developed chromatograms to x-ray films followed by scraping of radioactive spots and quantifying them. Relative amounts of various compounds in the fractions are indicated on the righthand side against numbered spots. Spots A-6, B-4, and C-5 represent unchanged cis-chlordane A-7 was a mixture of dichloro-chlordene and oxychlordane. A-3, B-3, C-4, and D-4 represent chlordene chlorohydrin. A-2, B-2, C-2, and D-2 were complex spots with the heptachlor diol as the major compound. A-l, B-l, C-l, and D-l were polyhydroxy derivatives or conjugates. Identities of other spots are not known. Recoveries in fractions A, B, C, and D were, respectively, 60.1%, 0.6%, 2.2%, and 2.9% of the applied radiocarbon. 

The pathways of metabolism of cis-chlordane appear to differ in these fish. Cichlids produce oxychlordane not produced by other fish. This may be due to the lack of formation of the intermediate, 1,2-dichlorochlordene in goldfish and bluegill (Fig. 6). 

Figure 6. Simplified scheme of metabolic pathways of cis-chlordane in fish (Route A), desaturation and epoxidation and (Route B), hydroxylations. Both routes are operative in cichlids (as in mammals). Goldfish and bluegills seem to...

Feces from injected (7.9 mg/kg) male rats were collected for one week and extracted with acetone yielding about 50% of the dose. Fish were treated with 5 ppb of the compound in water for 48 hr and then held in clean water for 11 days at the end of which they were extracted whole with organic solvents. Recovery of the compound applied to fish was 74.3%. Chromatographs (0.25 mm Silica gel GF-254) were developed with heptane twice. The figure shows relative abundance of metabolites in the two species. PC is photo-cis-chlordane. 

Table 4. Analysis of metabolites of photo-cis-chlordane in blue-gill as analyzed by TLC (silica gel GF-254, 0.25 mm) followed by X-ray autoradiography and scintillation counting (16).

Under similar conditions bluegill absorb cis-chlordane at a higher rate than the amphibian, Xenopus laevis. Photo-cis-chlordane, an isomer of cis-chlordane is absorbed at a higher rate than cis-chlordane by bluegill and goldfish. However, photo-cis-chlordane is eliminated faster than cis-chlordane by the fish. 

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