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Characterization of multiple binding sites for /sup 3/H-Estradiol-17. beta. -(. beta. -D-glucuronide) in rat liver plasma membranes: evidence consonant with identification of an organic anion carrier

Thesis/Dissertation ·
OSTI ID:6985771
The binding of /sup 3/H-Estradiol-17..beta..-(..beta..-D-glucuronide) (E/sub 2/17G) was examined in rat liver plasma membranes and two specific binding sites were identified. The evidence for multiplicity is derived from equilibrium, kinetic and inhibition experiments. Displacement and saturation experiments show that /sup 3/H-E/sub 2/17G binding is saturable. The absence of cooperative interactions at either site is suggested by the Hill coefficients (1.15 and 0.95 for Site 1 and Site 2 respectively). Kinetic dissociation experiments show that /sup 3/H-E/sub 2/17G binding is reversible and reveal two components (K/sub -1/'s = 1.4 and 0.024 min/sup -1/) to the dissociation process confirming the existence of multiple sites. The rate of association of /sup 3/H-E/sub 2/17G binding with plasma membranes is very rapid. Na/sup +/ is not required for binding of /sup 3/H-E/sub 2/17G. Ligands which selectively bind to Site 1 have been identified: these are bile acids, ouabain and testosterone glucuronide. The inhibition of /sup 3/H-E/sub 2/17G binding by organic anions provided evidence suggesting that Site 2 represents a hepatic organic anion carrier that is not shared by bile acids.
Research Organization:
Kentucky Univ., Lexington (USA)
OSTI ID:
6985771
Country of Publication:
United States
Language:
English

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