Page 75 - The Toxicology of Fishes

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Toxicokinetics in Fishes

Kevin M. Kleinow, John W. Nichols, William L. Hayton,
James M. McKim, and Mace G. Barron

CONTENTS
Introduction..............................................................................................................................................56
Basic Concepts.........................................................................................................................................57
Fish as Wet Vertebrates ..................................................................................................................57
The Environment............................................................................................................................58
Membranes and Xenobiotic Movement.........................................................................................60
Diffusion ...............................................................................................................................60
Specialized Membrane Transport.........................................................................................62
Absorption, Distribution, and Excretion .................................................................................................63
Xenobiotic Absorption ...................................................................................................................63
The Gills ...............................................................................................................................65
The Gastrointestinal Tract ....................................................................................................69
The Skin................................................................................................................................75
Xenobiotic Distribution..................................................................................................................77
Primary Determinants...........................................................................................................77
Local Distribution.................................................................................................................78
The Circulation.....................................................................................................................78
Xenobiotic Transport and Binding in Plasma......................................................................79
Tissue Affinity.......................................................................................................................80
Lipid Mobilization and Xenobiotic Redistribution in Reproducing Fish ........................... 81
Other Features of Distribution..............................................................................................82
Xenobiotic Elimination............................................................................................................................82
Branchial Excretion........................................................................................................................82
Biliary and Fecal Elimination........................................................................................................83
Contribution of the Liver......................................................................................................83
Metabolic and Physiological Impacts ..................................................................................85
Urinary Excretion...........................................................................................................................86
Tubular Anion Secretion.......................................................................................................88
Tubular Cation Secretion......................................................................................................89
Renal Clearance....................................................................................................................90
Dermal Excretion ...........................................................................................................................90
Elimination Via the Gametes .........................................................................................................91
Toxicokinetic Modeling...........................................................................................................................91
Clearance Concepts........................................................................................................................92
Hepatic Clearance.................................................................................................................92
Renal Clearance....................................................................................................................95
Branchial Clearance..............................................................................................................95
Compartmental Models for Fish....................................................................................................96
Volume of Distribution.........................................................................................................97
One-Compartment Model.....................................................................................................98
Two-Compartment Model...................................................................................................102
Utility of Compartmental Models for Fish........................................................................105

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