Abstract
Selectivity of tamsulosin and terazosin to functional α1-adrenoceptors was examined. Both drugs competitively inhibited the contractile responses to noradrenaline in different tissues where the responses were mediated through the α1D-, α1B- or α1L-subtype. Together with the affinities obtained in the binding study with cloned (α1a, α1b, α1d) and native (α1A and α1B) subtypes, the selectivity of tamsulosin was α1A>α1L, α1D>α1B. Terazosin had lower affinity at various subtypes than tamsulosin, but showed relatively high selectivity to the α1D-subtype. In the human prostate, tamsulosin was more than 30-fold higher in affinity than terazosin in functional and binding studies.
