TABLE 1

Parameter values obtained fitting the data of the agonist [3H](R)-PIA binding to A1 adenosine receptors, shown in Fig. 2, to different models Nonspecific binding was determined in the presence of an excess of (R)-PIA as described in Saura et al. (1996). The determined value for nonspecific binding was 0.029 pmol/mg protein/nM. Data are presented as mean ± S.E.M. values given by the regression program (GRAFIT).

Parameter Value
Two-state dimer receptor modela
   RTb 0.509 ± 0.008 pmol/mg protein
   c1 1.42 ± 0.18 nM
   c2 0.098 ± 0.014 nM2
[A]50 0.313 nM
Models in Fig. 7 (1:1 equation)
   R1 0.925 ± 0.019 pmol/mg protein
   K1 0.228 ± 0.023 nM
Two-independent-site receptor modelc
   R1 0.63 ± 0.05 pmol/mg protein
   K1 0.100 ± 0.014 nM
   R2 0.42 ± 0.04 pmol/mg protein
   K2 2.6 ± 0.9 nM

  • ↵ a P < 0.05 comparing models represented by a 1:1 equation and the two-state dimer receptor model

  • ↵ b Maximum binding = 2 × RT = 1.018 pmol/mg protein

  • ↵ c P > 0.30 comparing the classic “two-independent-site 1” and the two-state dimer receptor model