The objective of this proposal is to determine the stereochemistry of sulfate conjugation of chiral phenolic drugs, most notably sympathomimetic amine drugs, by the human phenolsulfotransferases (PSTs), the enzymatic mechanisms involved and its impact on the disposition of the enantiomers of these drugs. Most drugs of this class (isoproterenol, salbutamol, terbutaline) are used as racemic mixtures, although the pharmacologic properties of the individual enantiomers differ greatly. Based on preliminary observations, we have developed the hypothesis that sulfoconjugation of these drugs is enantioselective, tissue and isoenzyme specific and a key determinant of the availability of the enantiomers of these drugs at their multiple sites of action. This hypothesis will be tested directly in humans using tissue cytosols, isolated PST isoenzymes, cultured cell lines and in vivo.
In Aim 1 we will establish the kinetics (Km, Vmax) of sulfate conjugation of the individual enantiomers of these drugs, in particular by the human intestine and liver, but also by platelets and other tissues. We will use the cytosol as the PST source with 35S-labeled PAPS as the cosubstrate and stereospecific analytical methodology for the intact sulfate conjugates formed.
In Aim 2 we will isolate and purify they cytosolic PST isoenzymes, first from human intestine and liver and then from other tissues. We will characterize the specificity of the individual isoenzymes for sulfation of the enantiomers of the sympathomimetic amine drugs. Antibodies raised against the PST isoenzymes will be used in their characterization and quantitation in various tissues.
In Aim 3 w will establish the utility of human intestinal and hepatic cell lines as simple and reproducible models of stereoselective presystemic sulfate conjugation, the key determinant of the oral bioavailability of the enantiomers of these drugs.
In aim 4 we will examine the impact of stereoselective sulfate conjugation on the pharmacokinetics of sympathomimetic amine drugs in vivo in man in order to evaluate the clinical implications of our findings with human cytosol, purified PST isoenzymes and cell lines. Specifically, the proposed studies will determine the effect of stereoselectivity in sulfoconjugation on the availability of chiral drugs at their sites of action. More generally, these studies should lead to an improved understanding of the distribution, nature and function of human PSTs as well as provide a basis for studies of their binding/catalytic sites.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM046000-02
Application #
3305497
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1991-06-01
Project End
1995-05-31
Budget Start
1992-06-01
Budget End
1993-05-31
Support Year
2
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Medical University of South Carolina
Department
Type
Schools of Medicine
DUNS #
183710748
City
Charleston
State
SC
Country
United States
Zip Code
29425
Yao, Fude; Strauch, Mark A (2005) Independent and interchangeable multimerization domains of the AbrB, Abh, and SpoVT global regulatory proteins. J Bacteriol 187:6354-62
Hartman, A P; Wilson, A A; Wilson, H M et al. (1998) Enantioselective sulfation of beta 2-receptor agonists by the human intestine and the recombinant M-form phenolsulfotransferase. Chirality 10:800-3
Wilson, A A; Wang, J; Koch, P et al. (1997) Stereoselective sulphate conjugation of fenoterol by human phenolsulphotransferases. Xenobiotica 27:1147-54
Eaton, E A; Walle, U K; Wilson, H M et al. (1996) Stereoselective sulphate conjugation of salbutamol by human lung and bronchial epithelial cells. Br J Clin Pharmacol 41:201-6
Walle, T; Eaton, E A; Walle, U K et al. (1996) Stereoselective metabolism of RS-albuterol in humans. Clin Rev Allergy Immunol 14:101-13
Lewis, A J; Kelly, M M; Walle, U K et al. (1996) Improved bacterial expression of the human P form phenolsulfotransferase. Applications to drug metabolism. Drug Metab Dispos 24:1180-5
Walle, T; Eaton, E A; Walle, U K (1995) Quercetin, a potent and specific inhibitor of the human P-form phenosulfotransferase. Biochem Pharmacol 50:731-4
Walle, T; Walle, U K; Shwed, J A et al. (1994) Human phenol sulfotransferases: chiral substrates and expression in Hep G2 cells. Chem Biol Interact 92:47-55
Walle, U K; Pesola, G R; Walle, T (1993) Stereoselective sulphate conjugation of salbutamol in humans: comparison of hepatic, intestinal and platelet activity. Br J Clin Pharmacol 35:413-8
Walle, T; Walle, U K; Thornburg, K R et al. (1993) Stereoselective sulfation of albuterol in humans. Biosynthesis of the sulfate conjugate by HEP G2 cells. Drug Metab Dispos 21:76-80

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