Biomedical subjects
Publications and source records attributed to W Fürst.
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Two metabolites of Falimint which have not been elucidated till now were demonstrated to be the glucuronides of 2-acetamino-4-nitro-phenol and 2-amino-4-nitro-phenol. A further metabolite was found by isolation with adsorption resins and identified to be the sulfuric acid conjugate of 2-amino-4-nitro-phenol.
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The enzymic degradation of a number of sphingolipids in the lysosomes is stimulated by small acid glycoproteins named activator proteins. We purified and sequenced a new protein, called component C, which seems to be related to sulfatide activator and to a recently described activator of glucosylceramidase (A1 activator) (Kleinschmidt, T., Christomanou, H. & Braunitzer, G. (1987) Biol. Chem. Hoppe-Seyler 368, 1571-1578). It consists of 78 amino acids and carries one carbohydrate chain at aparagine 20. Component C shows 21.5% sequence homology to sulfatide activator and 34.2% homology to A1 activator. Structural similarities between these three proteins have also been detected. Recently the cDNA sequence of the sulfatide activator precursor has been published (Dewji, N.N., Wenger, D.A. & O'Brien, J.S. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 8652-8656). We could align the protein sequences of sulfatide activator, A1 activator and component C with that of this large precursor protein. After minor corrections of the DNA sequence we obtained total fit. Thus it seems that three different proteins are derived from the sulfatide activator precursor by proteolytic processing. Possible processing sites were found on the precursor at sites adjacent to the N-termini and C-termini of the mature proteins. The processing of sulfatide activator was studied by Fujibayashi and Wenger (Fujibayashi, S. & Wenger, D.A. (1986) Biochim. Biophys. Acta 875, 554-562). Their data support our assumption that processing occurs by simultaneous cleavage at all possible sites.
The use of sonicated liposomes for the characterization of the transport behaviour of basic drugs is described. The rate of permeation depends mostly on the lipophilic character of the drugs.
Based on previous in vitro studies it could be shown that ion-pair-formation with the lipophilic hexylsalicylic acid (1) influences the pharmacokinetics of the hydrophilic drug pholedrine (2) which is ionized in all physiological media. After oral combination with 1 an increase of the AUC of 2 could be observed. This finding is due both to the increase of the absorption of 2 and to the decrease of the elimination of 2. After i.v. application the high biotransformation rate of 2 prevents an influence of 1.
Based on in vitro results it was found that the pharmacokinetic parameters of the hydrophilic drug bretylium (2) can be influenced by an ion-pair-formation with the lipophilic hexylsalicyclic acid (1). After simultaneous i.v. application of 1 and 2 on rabbits a significant increase of the AUC of 2 was observed. Under these conditions a marked increase of the AUC and the MRT of 1 was also obtained, since the blood levels of 2 are high enough for such an influence. A combined rectal application of 1 and 2 causes an increase of the AUC of 2.
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