Thiopental binding to human serum albumin in the presence of halothane.
In vitro thiopental binding (substrate concentration 0.04.10(-3) M = 10 micrograms/ml) to 1% human serum albumin (HSA) increased significantly from 40.2% (= control) to 47.3% in the presence of 1.18.10(-3) M = 2.84 vol% halothane. A 4-fold higher halothane concentration (4.71.10(-3) M) had an even greater effect with an increase in the thiopental fraction bound to 55.5%. With a constant HSA concentration (1% or 5%) and thiopental concentrations in the range 0.01-1.5.10(-3) M or 0.01-0.38.10(-3) M, respectively, the halothane effect (increase in thiopental binding) was always evident, as well as in other experiments with constant thiopental concentration (0.04.10(-3) M) and variation in the HSA concentration (0.5-10%). Two classes of binding sites for thiopental were apparent at the HSA molecule. In the control experiments the following binding parameters were found: n1 = 0.01, k1 = 181.10(3) M-1; n2 = 45.73, k2 = 0.08.10(3) M-1, K = 5.47.10(3) M-1. In the presence of halothane the binding parameters changed as follows: n1 = 0.14, k1 = 29.4.10(3) M-1; n2 = 11.68, k2 = 0.42.10(3) M-1, K = 9.02.10(3) M-1.
Büch
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HP
Institut für Pharmakologie und Toxikologie, Universität des Saarlandes Homburg/Saar, FRG.
Altmayer
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Büch
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D001665:Binding Sites; D006221:Halothane / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D008433:Mathematics; D011485:Protein Binding / Q000187:drug effects; D012709:Serum Albumin / Q000378:metabolism*; D013268:Stimulation, Chemical; D013874:Thiopental / Q000008:administration & dosage / Q000378:metabolism*
D012709:Serum Albumin; D013874:Thiopental; D006221:Halothane