rH2Receptor | [125I]APT | Histamine,Ki | |
---|---|---|---|
Bmax | KD | ||
fmol/mg | nM | μM | |
Wild type, untreated | 2734 ± 725 | 0.76 ± 0.18 | 242 ± 40 |
Wild type, pretreated | 4246 ± 894 | 1.51 ± 0.36 | 452 ± 100 |
R116A, pretreated | 586 ± 64 | 1.02 ± 0.19 | 79 ± 11** |
R116N, pretreated | 782 ± 182 | 1.16 ± 0.20 | 37 ± 8** |
Cell homogenates of transiently transfected HEK-293 cells, untreated or pretreated with 100 μM ranitidine directly after transfection, were incubated with increasing concentrations of [125I]APT to determine the KD value or with 0.3 nM [125I]APT in the presence of increasing concentrations of histamine. Ki values were obtained from the respective IC50 values. Data shown are mean ± S.E. from at least three independent experiments. The asterisks indicate a significant difference from pretreated HEK-293 cells expressing the wild-type H2 receptor (see Materials and Methods).