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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 305 (1978), S. 41-50 
    ISSN: 1432-1912
    Schlagwort(e): Red Blood Cells ; Rats ; β-Adrenoceptors ; Adenyl cyclase ; (3H) (−)Dihydroalprenolol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary For the direct characterization of β-adrenoceptors in membrane preparations from the reticulocyte rich blood of rats treated with acetyl phenylhydrazide the β-adrenergic antagonist ligand (3H)(−)dihydroalprenolol (DHAP) was used. 1. Specific binding of DHAP demonstrated one type of binding site in these membrane preparations. There was no evidence for negative co-operativity between the sites. A mean K D -value amounting to 6.51\+-0.8 nM (n=15) was calculated from equilibrium experiments; a similar K D -value (8.25 nM) was evaluated from the ratio of the rate constants of the dissociation and association reactions. In preparations of reticulocyte rich blood (53% reticulocytes) a mean density of DHAP binding sites of 0.602\+-0.05 pmoles/mg protein (n=15) was determined. The respective value in membrane preparations from reticulocyte poor blood, i.e. from untreated animals (2% reticulocytes), amounted to only 0.224\+-0.03 pmoles/mg protein (n=5) whereas the mean K D -value remained unaltered (K D =6.84\+-2.2 nM; n=5). 2. Specific binding sites for DHAP in membranes from reticulocyte rich blood can be looked at as true \gb-adrenoceptors: Specific binding of DHAP was competitively inhibited by β-adrenoceptor agonists and antagonists according to the structural specificity and stereospecificity of these compounds. The K D -values for agonists increased in the order isoprenaline 〈 adrenaline 〈 noradrenaline 〈 phenylephrine, the (−)enantiomers being significantly more potent than the respective (+)enantiomers. The same was true also for β-adrenoceptor antagonists. 3. Using the highly purified enantiomers of fenoterol, a compound with 2 asymmetric centres, it was demonstrated that the 1R/1\t'R isomer was highly active while the enantiomer 1S/1\t'S did not show any affinity for \gb-adrenoceptors. 4. When the K D -values evaluated from binding experiments were compared to the respective K a - and K i -values obtained from adenyl cyclase assays in the same membrane preparations there resulted direct correlations (K D \~-K a or K i ). The identity of these values for \gb-adrenoceptor agonists is in favour of an optimal coupling state of the \gb-adrenoceptor-adenyl cyclase-system in immature red blood cells from rats.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 55 (1977), S. 457-459 
    ISSN: 1432-1440
    Schlagwort(e): Human plasma glycosphingolipids ; Acute hepatitis ; Hyperlipoproteinemia ; Glycosphingolipide im menschlichen Blutplasma ; Akute Hepatitis ; Hyperlipoproteinämie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Im menschlichen Blutplasma kommen hauptsächlich vier neutrale Glycosphingolipidfraktionen vor: Monohexosyl-, Dihexosyl-, Trihexosyl- und Tetrahexosylceramid. Bei Patienten mit akuter Hepatitis (n=21) sind in der akuten Phase die vier Glycosphingolipidfraktionen im Plasma gegenüber einem gesunden Kontrollkollektiv (n=23) erhöht. Mit Ausnahme der Trihexosylceramidfraktion läßt sich die Erhöhung statistisch sichern. Gleichzeitig kommt es in der akuten Phase der Hepatitis zu einer statistisch signifikanten Cholesterin- und Triglyceriderhöhung. Es wird gefolgert, daß die Erhöhung der Glycosphingolipide im Plasma bei der akuten Hepatitis im Zusammenhang mit der Fettstoffwechselstörung auftritt und daß ein Teil der Glycosphingolipide des Plasmas in der Leber synthetisiert wird entsprechend den VLDL.
    Notizen: Summary There are mainly four neutral glycosphingolipids in human blood plasma: Monohexosyl, dihexosyl, trihexosyl and tetrahexosyl ceramide. In patients with viral hepatitis (n=21) during the acute phase all four fractions of plasma glycosphingolipids were elevated compared to healthy subjects (n=23). With the exception of trihexosyl ceramide all fractions demonstrated statistically striking elevations in the acute phase of viral hepatitis. Simultaneously in the acute phase of hepatitis triglycerides and cholesterol in serum were significantly increased. It is concluded the elevation of glycosphingolipid levels in plasma is a metabolic consequence of hyperlipoproteinemia. Furthermore it is supposed that a part of plasma glycosphingolipids is synthezised de novo by the liver like VLDL.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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