Büch HP, Altmayer P, Büch U. Thiopental binding to human serum albumin in the presence of halothane.
Acta Anaesthesiol Scand 1990;
34:35-40. [PMID:
2309539 DOI:
10.1111/j.1399-6576.1990.tb03037.x]
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Abstract
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.
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