The chromatographic determination of oxalyl thiolesters in mammalian tissues and their possible role as metabolic mediators

In the present work, a chromatographic assay for oxalyl thiolesters (OTEs) in physiological materials is presented. OTEs are the direct products of the probable physiological reactions catalyzed by the peroxisomal oxidases D-amino acid oxidase and L-hydroxy acid oxidase. OTEs are believed to be important metabolic effectors and may function as part of the intracellular messenger system for hormones such as insulin and growth factors. Based on previous correlations of insulin activity and inhibition of these oxidases, it has been proposed that OTEs function as negative effectors for insulin and growth factors.;The assay for OTEs is based on the previous discovery that the oxalyl group on the OTE transfers very rapidly from one thiol to another. However, when a tissue is homogenized in the presence of a ;Using this assay, OTEs have been found in various rat tissues at concentrations as high as 65 nmol/g wet weight of tissue. In bovine lymphocytes, the average concentration found was 8 nmol/g wet weight, while an average of 3 nmol/g wet weight was found in normal Swiss 3T3 fibroblasts. Cell proliferation stimulators that are known to cause insulin-like effects in certain systems were predicted to lower OTE concentrations in bovine lymphocytes relative to control cells. The effect of several mitogens on OTE levels in lymphocytes was investigated. Concanavalin-A (CON-A) was shown to lower lymphocyte OTE concentrations by an average of 44% or 58% depending on the concentration of CON-A used. Costimulation with phytohemagglutinnin (PHA) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) also lowered normal lymphocyte OTE concentrations by an average of 55%. Stimulation of lymphocytes with either PHA or TPA alone only decreased OTE levels by an average of 23% and 28% respectively. OTE levels in Swiss 3T3 fibroblasts transformed by SV-40 virus were lowered by an average 74% compared to normal 3T3 cells.