Two major groups of molecules are sulfated in the body; small molecules such as drugs, hormones and environmental chemicals, as well as large molecules such as proteins and glycosaminoglycans. The sulfate conjugation reaction is catalyzed by sulfotransferases utilizing adenosine 3' -phosphate 5' -phosphosulfate (PAPS) as the sulfate donor. Brachymorphic mice have a defect in PAPS synthesis, and thus undersulfate glycosaminoglycans which results in joint and skeletal defects. The sulfation of xenobiotics is characterized as being a high-affinity, how- capacity pathway. The low-capacity sulfation of xenobiotics in rats is due to a limited availability of PAPS, which in turn is limited by the availability of sulfate. Molybdate also decreases hepatic levels of PAPS and sulfate. Molybdenum is known to produce joint problems, which can be prevented by sulfate and methionine. Because joints are largely cartilage and a major constituent of cartilage is sulfated glycosaminoglycans, we propose to test the hypothesis that joint problems produced by molybdate are due to an undersulfation of the glycosaminoglycans. There is also evidence in the literature that drugs that are sulfated decrease the sulfation of glycosaminoglycans and produce teratological effects in the cartilage-skeletal system.
Six specific aims will be addressed in the proposed research. We plan to test the hypotheses that: (1) PAPS concentrations can be decreased by molybdate, (2) PAPS depletion by molybdate is a useful tool for determining the importance of sulfation in toxicology, (3) molybdate interferes with glycosaminoglycan sulfation, (4) chlorinated phenols inhibit glycosaminoglycan synthesis by inhibiting sulfation, (5) chemicals that are sulfated decrease glycosaminoglycan sulfation, (6) and chemical interference of glycosaminoglycan sulfation is not unique to rats. Methods to be employed are enzymatic quantitation of PAPS, HPLC- ion chromatographic analysis of sulfate and use of isotopes to quantitate glycosaminoglycan synthesis. Scientifically these investigations are intriguing because they may reveal novel mechanisms for toxic effects of chemicals via impairment of the sulfation of glycosaminoglycans. They are also of potential medical significance, because sulfation of the glycosaminoglycans in cartilage is essential for the proper functioning of joints, and joint ailments are the number one cause of debilitation in the aging American population. Therefore, the long-term goal of these studies is to determine if and how chemicals interfere with cartilage formation and thus joint disease.
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