Many chemical substances have been shown to influence renal function (Commandeur
and Vermeulen 1990). The production of mild and reversible changes is
pharmacologically important in the development of diuretics and renin - angiotensin
inhibitors in contrast irreversible changes may occur following administration of some
drugs and chemicals. There are several reasons for the susceptibility of the kidneys to
injury. First renal blood flow is approximately 25% of cardiac output and delivers large
quantities of blood to the kidneys especially the cortex. Second the kidneys have the
ability to concentrate the fluid passing through the tubules such that the concentrations of
certain drugs and chemicals may increase 100–1000-fold at certain regions e.g. proximal
tubule. Transport processes for cationic and anionic molecules located in the proximal
tubule may be blocked by or used by chemicals to gain entry into the renal epithelial
cells. Third the presence in the proximal tubules of mixed-function oxidase enzymes
which have the potential to transform harmless substances into more reactive metabolites
renders this segment of the tubule vulnerable to injury.