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. 2005 Oct 17;146(8):1119–1129. doi: 10.1038/sj.bjp.0706419

Table 1.

[3H]DPCPX competition-binding parameters against various agonists at human adenosine A1 receptor stably expressed in CHO cell membranes

Temperature Agonist Treatment pKHa pKLb FHc nHd ne
25°C R-PIA ADAf 8.82±0.08g 6.42±0.13 0.68±0.03 0.54±0.03h 3
    Gpp(NH)pi 7.72±0.06g 6.42±0.13 0.68±0.03 0.72±0.05h 3
    Ureaj 7.71±0.06 6.42±0.13 0.68±0.03 0.63±0.04h 3
  CHA ADA 8.64±0.09 6.15±0.19 0.69±0.04 0.52±0.05h 3
    Gpp(NH)p 7.21±0.08 6.15±0.19 0.69±0.04 0.77±0.08h 3
    Urea ND 6.15±0.19 NA 1.17±0.13 3
               
37°C R-PIA ADA 8.00±0.23 6.39±0.20 0.51±0.11 0.63±0.07h 3
    Gpp(NH)p 7.16±0.14 6.39±0.20 0.51±0.11 1.05±0.14 3
    Urea ND 6.39±0.20 NA 1.17±0.17 3
  CHA ADA 8.22±0.14 6.37±0.14 0.54±0.06 0.55±0.05h 3
    Gpp(NH)p 7.08±0.12 6.37±0.14 0.54±0.06 0.80±0.09h 3
    Urea ND 6.37±0.14 NA 0.95±0.06 3
  Adenosine Urea ND 5.66±0.05 NA 0.98±0.09 3

Assays were performed for 90 min in 50 mM Tris(HCl) buffer at the indicated temperatures. Nonspecific binding was defined using 10 μM R-PIA.

a

Negative logarithm of the apparent dissociation constant for the high-affinity agonist-binding state, determined by global nonlinear regression analysis of all three treatment groups to a common binding model (see Methods).

b

Negative logarithm of the apparent dissociation constant for the low-affinity agonist-binding state, determined by global nonlinear regression analysis of all three treatment groups to a common binding model. An extra-sum-of squares (F-test) concluded that a single value of the parameter could describe all the curves.

c

Fraction of the high-affinity agonist-binding state, determined by global nonlinear regression analysis of all three treatment groups to a common binding model. An extra-sum-of squares (F-test) concluded that a single value of the parameter could describe all the curves where a high-affinity state was evident.

d

Hill slope, determined by nonlinear regression analysis to a logistic function.

e

Number of experiments.

f

Membranes were pretreated with 10 U ml−1 ADA during preparation, and assays subsequently performed in the presence of 0.1 U ml−1 ADA.

g

Significantly different (P<0.05; Student's t-test) from the corresponding value at 37°C.

h

Significantly different (P<0.05; F-test) from 1.

i

As in footnote f above, but with the addition of 100 μM Gpp(NH)p.

j

Membranes were pretreated with 7 M urea during preparation.

ND, not determined.

NA, not applicable.