Table 2.
pA2 or pKb values of silodosin and other α1-AR antagonists for noradrenaline-induced contraction in the isolated rabbit prostate, urethra and bladder, and in the isolated rat spleen and thoracic aorta
| Compound |
pA2 or pKbvalues |
||||
|---|---|---|---|---|---|
|
α1A-AR |
α1B-AR |
α1D-AR |
|||
| Prostatea | Urethraa | Bladder trigonea | Spleenb | Thoracic aortab | |
| Silodosin | 9.60 ± 0.05c | 8.71 ± 0.09 (0.98 ± 0.32) | 9.35 ± 0.15c | 7.15 ± 0.05 (0.67 ± 0.09*) | 7.88 ± 0.05 (1.00 ± 0.18) |
| Tamsulosin hydrochloride | 9.93 ± 0.07c | 9.00 ± 0.06 (1.16 ± 0.27) | 9.48 ± 0.14c | 8.64 ± 0.06 (0.61 ± 0.18*) | 9.82 ± 0.06 (0.91 ± 0.20) |
| Naftopidil | 6.69 ± 0.05c (1.13 ± 0.21) | 6.48 ± 0.11 (0.93 ± 0.39) | 6.80 ± 0.07 (0.91 ± 0.25) | 6.30 ± 0.07 (0.69 ± 0.23) | 7.48 ± 0.06 (1.14 ± 0.23) |
| Prazosin hydrochloride | 7.91 ± 0.02 (1.08 ± 0.09) | 7.96 ± 0.04 (0.85 ± 0.13*) | 8.10 ± 0.05 (0.97 ± 0.18) | 9.34 ± 0.13 (0.56 ± 0.26*) | 9.17 ± 0.06 (1.11 ± 0.23) |
Notes: Each value in the table presents mean ± standard error of 4–5 animals. Each value in a parenthesis presents the slop of the Schild plot. a) Rabbits, b) Rats, c) pK;
value.
Significantly different from the unity at P < 0.05 by paired-t test.
Abbreviations: pA2, negative logarithmic value of molar concentration of antagonistic blockers necessary to parallel shift 2 times the independent stimulant concentration-reaction curve to the higher concentration side; pKb value, negative logarithmic value of dissociation constant for binding of antagonistic blockers to receptors.
Reproduced with permission from Yakugaku Zasshi Vol 126 Special issue. Copyright © 2006 Pharmaceutical Society of Japan.23