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In order to describe the analysis we extend slightly the
nomenclature used above; this nomenclature will apply only to the
specific two-ligand, two-site isotherm to be "linearized." Bg and Bg
are the total concentrations of specifically bound [ Hjcorticosterone
and "cold" dexamethasone, respectively. BgR and BgT are the
concentrations of [ H]corticosterone bound to the putative receptors and
to CBG (transcortin), respectively. (Thus, Bg = BgR + Bgy). B^^ is
the total concentration of all binding sites, composed of Bg putative
glucocorticoid receptors and Tg transcortin binding site
(BMAX = B0 + V- KdL describes (approximately) the common affinity of
3
[ Hjcorticosterone for both the receptor and CBG binding sites, and K^g
is the equilibrium constant for the binding of dexamethasone to the
glucocorticoid receptor sites. Fg and Fg are the concentrations of
3
unbound (free) [ Hjcorticosterone and "cold" dexamethasone,
respectively.
From the mass-action equations (cf. equations 3-8 and 3-9 above) we
have the following:
(Bg-BLR-Bg)Fc = ^gBg,
(3-13)
%BLR-Bc)FL = KdLBLR
(3-14)
(VBLl)FL = KdLBLT
(3-15)
and, adding equations (3-14) and (3-15) we get
(BMAX-BL-BC>FL = KdlA-
(3-16)