Table 1

Affinity of tamsulosin and its analogs for rat tissuealpha-1 adrenoceptor subtypes

Rat LiverRat Kidney
Hill-slope−logKi Hill-slope−logKi high−logKi low% High-affinity sites
Tamsulosin1.01  ± 0.079.38  ± 0.080.52  ± 0.0710.53  ± 0.158.64  ± 0.2045  ± 7
M10.88  ± 0.048.66  ± 0.050.55  ± 0.039.86  ± 0.218.06  ± 0.1547  ± 7
M21.03  ± 0.068.03  ± 0.020.39  ± 0.109.63  ± 0.547.39  ± 0.2236  ± 2
M31.10  ± 0.098.15  ± 0.020.55  ± 0.029.34  ± 0.217.62  ± 0.1438  ± 3
M40.90  ± 0.079.45  ± 0.030.53  ± 0.0410.62  ± 0.098.84  ± 0.0245  ± 5
5-Methylurapidil0.92  ± 0.106.28  ± 0.390.54  ± 0.038.11  ± 0.116.32  ± 0.0550  ± 4
(+)-Niguldipine1.00  ± 0.056.90  ± 0.100.39  ± 0.029.23  ± 0.056.87  ± 0.0347  ± 1
WB 41011.10  ± 0.058.15  ± 0.080.69  ± 0.019.54  ± 0.088.18  ± 0.0748  ± 9

Data are the means ± S.E.M. of three to five experiments. Hill-slopes for the rat kidney are derived from a monophasic fit, whereas −log K i high, and −logK i low and percentage of high-affinity sites in this tissue were estimated from a biphasic fit. In the rat kidney, the biphasic fit was significantly better than the monophasic fit (P < .05) as judged by an F test. A graphical representation of the data is shown in figures 1 and 2. Data for 5-methylurapidil, (+)-niguldipine and WB 4101 generated in our laboratory with identical methods are taken from (Michel et al., 1993, 1996;Büscher et al., 1996; Chess-Williams et al., 1996) and are shown for reference purposes.