Metabolic Interactions of Pesticides - Pesticide Biotransformation and Disposition - page 147

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CHAPTER

Metabolic Interactions of Pesticides

Ernest Hodgson
North Carolina State University, Raleigh, NC, USA

Outline
Chemical Factors Affecting Pesticide Metabolism: Introduction

149

Induction 151

Induction of Microsomal Enzyme Activity 151

Induction of Other Enzymes 160

Mechanism of Induction 160

Inhibition 161

Types of Inhibition and Experimental Demonstration 161

In Vivo Symptoms 161

Distribution and Blood Levels 161

Effects on in Vitro Metabolism Following in Vivo Treatment 162

In Vitro Effects 162

Synergism and Potentiation 164

Antagonism 165

Pesticides as Inhibitors 165

Biphasic Effects: Inhibition and Induction 167

Activation 168

Hepatotoxicity 169

Conclusions 170

References 170

CHEMICAL FACTORS AFFECTING PESTICIDE METABOLISM:
INTRODUCTION

Although the study of the metabolism and toxicity of pesticides is simplified by con-
sidering single compounds, humans and other living organisms are not exposed in this
way; rather, they are exposed to many xenobiotics simultaneously, involving different
portals of entry, modes of action, and metabolic pathways. Because they bear directly
on the problem of toxicity-related interactions between various xenobiotics, metabolic
interactions between exogenous compounds are important in the study of toxicity.
This is particularly true in the case of pesticides, which are frequently formulated, and
used, as mixtures. Also of importance in considerations of pesticide toxicity and safety
are metabolic interactions between pesticides and endogenous metabolites.