Page 86 - The Toxicology of Fishes

66 The Toxicology of Fishes

A 8 7 I
BRANCHIAL CLEARANCE (L/kg hr) 6 5 4 3 2 1 D E 3 4 F 5 G H J K L M N

0 1 A B C 2 O
0 1 2 3 4 5 6 7 8

B
3
13 14
8 10 11 12 16 15
7
LOG k (1/hr) 2 3 4 5 6
2
1
1

0
0 1 2 3 4 5 6 7 8
CHEMICAL LOG K
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FIGURE 3.4 Relationship between the branchial uptake of chemicals by rainbow trout and guppies, and chemical
hydrophobicity expressed as the log of the octanol–water partitioning coefficient. The uptake rate for rainbow trout is
expressed as a clearance constant; that for guppies is given as the log of the uptake rate constant from water when pH <
chemical pK a . (A) Rainbow trout sublethal exposures: A, ethyl formate; B, ethyl acetate; C, 1-butanol; D, nitrobenzene;
E, p-cresol; F, chlorobenzene; G, 2,4-dichlorophenol; H, 2,4,5-trichlorophenol; I, 1-decanol; J, 1-dodecanol; K, pentachlo-
rophenol; L, hexachlorobenzene; M, 2,2′,5,5′-tetrachlorobiphenyl; N, dinitrophenol; O, mirex. Rainbow trout lethal expo-
sures: 1, benzaldehyde; 2, 2,4-dinitrophenol; 3, MS-222; 4, malathion; 5, 1-octanol. (Data from Erickson and McKim,
1990a.) (B) Guppy sublethal exposures: 1, butyric acid; 2, phenol; 3, benzoic acid; 4, 4-phenylbutyric acid; 5, 2,4-dichlo-
rophenol; 6, 2-sec butyl-4,6-dinitrophenol; 7, 3,4,-dichlorobenzoic acid; 8, 2,6-dibromo-4-nitrophenol; 9, 2,4,5-trichlo-
rophenol; 10, 2,4,6-trichlorophenol; 11, 2,3,4,6-tetrachlorophenol; 12, tetrachloroverathrol; 13, pentachlorophenol; 14,
pentachloroanisol; 15, 2,4,6-trichloro-5-phenylphenol; 16, DDT. (Adapted from Saarikoski, J. et al., Ecotoxicol. Environ.
Saf., 11, 158–173, 1986.)

carboxylic acids, Saarikoski et al. (1986) found a similar relationship between absorption rate and log
K in the guppy (Poecilia reticulata) (Figure 3.4B). Additional studies with a homologous series of
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chlorinated ethanes in the channel catfish (Ictalurus punctatus) (McKim et al., 1994), fathead minnow
(Pimephales promelas) (Lien et al., 1994), and lake trout (Salvelinus namaycush) (McKim et al., 1999a)
have extended these observations to other species.
Several physiological and chemical factors may account for these trends in gill uptake with chemical
hydrophobicity. Gobas et al. (1986) proposed that branchial uptake was regulated by chemical partitioning
into lipid phases and diffusion through lipid membranes and associated aqueous layers. Both McKim
et al. (1985) and Saarikoski et al. (1986) attributed increases in absorption between log K 1 and 3 to
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greater membrane permeability for the more lipophilic compounds. Opperhuizen et al. (1985) suggested
that gill membranes inhibit the uptake of lipophilic compounds that exceed a critical molecular volume.
Other researchers, noting a downward trend in bioconcentration factors (BCFs; defined as the ratio of
the chemical concentration in the fish to that in water) for compounds with log K values greater than
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