The modification of proteins, by covalent or noncovalent means, represents an important early event in cell death produced by therapeutic, industrial or eenvironmental chemicals. Recent advances in immunological methodology have provided insight into the mechanisms of reactive-metabolite initiated cell damage. Several model compounds have been favored for these studies, including the nephrotoxic cysteine conjugates and the hepatotoxic analgesic, acetaminophen. The specific goals of this proposal are to examine: 1) the structural and biochemical properties of two members of the stress protein family (mitochondrial HSP60 and PBP74) in response totoxicant adminstration, 2) the adaptive and homeostatis cellular responses to toxicant exposure, 3) Specific mitochondrial and cellular alterations produced by exposure to acetaminophen or a nephrotoxic cysteine conjugate The experimental designs for each of these goals are based on techniques that we have used previously, for example, in the identification of covalently modified proteins during nephrotoxicity. These incoude the use of:- a) immunoblot procedures with antisera or monoclonal antibodies to adducted or unmodified proteins; b) conventionalprotein isolation methods to purify modified proteins; c) protein chemistry and mass spectrometry techniques to N-terminally sequence and identify proteins, and, d) molecular biological and confocal microscopy studies to examine cellular and mitochondrial responses to toxicant exposure. The potential long-term health ramifications are based on a more complete understanding of the relationship between reactive metabolite-mediated cell injury and the cellular protective response to harmful chemicals. A thorough biochemical and cell biological understanding of these events will ultimately allow parmacological, and other, interventions. Consequently, the harmful effects of a deleterious agent, for example in an occupational health setting, may be treated and avoided.