Geology topics

W. L. Hayton

Publications and source records attributed to W. L. Hayton.

4 recordsLinked to original sources

USGS2009

Metabolism of pentachlorophenol by fish

Interspecies variability in the metabolism of pentachlorophenol (PCP) was investigated by exposing rainbow trout, fathead minnows, sheepshead minnow, firemouth, and goldfish to water-borne super(14)C-PCP for 64 h. The amounts of metabolites in bile and exposure water were species-dependent; all of the metabolites excreted into the water were sulphate conjugates while bile was enriched in glucuronide conjugates. Biliary excretion accounted for less than 30% of the total PCP metabolites. Biliary metabolites alone were a poor indication of the metabolites produced and of the major routes of elimination.

Xenobiotica↗

USGS1990

Effect of pH on the accumulation kinetics of pentachlorophenol in goldfish

The kinetics of accumulation of pentachlorophenol (PCP) at various pH values were investigated to explore how pH-dependent accumulation might influence PCP toxicity. Goldfish (Carassius auratus) were exposed to 5 μg PCP/L in a static system buffered with 7.5 mM bicine or N,N -bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (BES) at pH 7.0, 8.0, or 9.0. The amount of PCP in the fish, concentration of PCP in water, and the total amount of metabolites in the system were measured after exposure of fish from 1 to 96 hr. Equations for these variables based on a two compartment pharmacokinetic model were fitted simultaneously to the data using NONLIN, which uses an iterative nonlinear least squares technique. Uptake clearance, metabolic clearance, and apparent volume of distribution of PCP decreased as pH increased. The decrease in PCP accumulation with increased pH was not due solely to a pH-induced decrease in uptake. In addition, the distribution of PCP within the fish was altered by changes in the external pH. The pH-associated changes in distribution may have altered access of PCP to sites of metabolism, thereby altering the metabolic clearance. The pH-related changes in the pharmacokinetics of PCP resulted in a decrease in its bioconcentration factor with an increase in pH and account both for the decreased capacity of the fish to accumulate PCP and for its reduced LC50.

Archives of Environmental Contamination and Toxico↗

USGS1990

Pharmacokinetic modeling in aquatic animals. 1. Models and concepts

While clinical and toxicological applications of pharmacokinetics have continued to evolve both conceptually and experimentally, pharmacokinetics modeling in aquatic animals has not progressed accordingly. In this paper we present methods and concepts of pharmacokinetic modeling in aquatic animals using multicompartmental, clearance-based, non-compartmental and physiologically-based pharmacokinetic models. These models should be considered as alternatives to traditional approaches, which assume that the animal acts as a single homogeneous compartment based on apparent monoexponential elimination.

Aquatic Toxicology↗

USGS1989

Disposition of pentachlorophenol in rainbow trout (Salmo gairdneri): Effect of inhibition of metabolism

The accumulation kinetics of pentachlorophenol (PCP) were investigated in rainbow trout ( Salmo gairdneri ) in the absence and presence of 25 mg/1 salicylamide, an inhibitor of PCP metabolism. After exposure to 5 μg/1 PCP over 1–96 h, the amount of PCP in the whole fish, its concentration in water and the total amount of metabolites (water, whole fish and bile) were measured. Equations for these variables, based on a two compartment pharmacokinetic model, were fitted simultaneously to the data using the computer program NONLIN, which uses an iterative nonlinear least squares technique. Salicylamide decreased the metabolic clearance of PCP, which resulted in an increase in the bioconcentration factor (BCF); this increase was partially offset by a salicylamide-induced decrease in the apparent volume of distribution of PCP. A clearance-volume compartment model permitted partitioning of the BCF in terms of the underlying physiologic and biochemical processes (uptake clearance, metabolic clearance and apparent volume of distribution). With this approach the BCF can be categorized as either dependent (e.g., PCP) or independent of uptake and metabolism (elimination) based on the relative sizes of the clearances for uptake and metabolism. Inhibition of PCP metabolism resulted in a loss of its dependence on uptake and metabolism. The BCF estimated as the apparent volume of distribution may be useful for assessment of the risk associated with exposure and bioaccumulation potential, as elimination is generally quite variable among aquatic species.

Aquatic Toxicology↗