Abstract

This study was performed to assess the affinity of tamsulosin to the α<sub>1L</sub>- in addition to α<sub>1B</sub>-adrenoceptor (α<sub>1</sub>-AR) subtypes coexisting in the canine aorta using the radioligand binding assay. The antagonistic effects of this drug on contraction of the rat aorta were also assessed, and the results were compared with those obtained with prazosin, amosulalol, labetalol, ketanserin, clonidine and propranolol. The pKi value of tamsulosin to the α<sub>1L</sub>-subtype was lower than those of prazosin and HV-723, but higher than those of amosulalol, ketanserin and labetalol. The pKi value of tamsulosin for the α<sub>1B</sub>-subtype in the canine aorta was similar to that of prazosin. However, this drug showed a higher pKi value than amosulalol, HV-723, labetalol and ketanserin. On the other hand, the order of inhibition potencies for contraction of the rat aorta by phenylephrine was as follows: prazosin > tamsulosin > amosulalol > HV-723 > labetalol > ketanserin > clonidine > propranolol. Thus, although the affinity of tamsulosin to the α<sub>1B</sub>-AR subtype in the canine aorta was as high as that in the bovine prostate reported in our previous study, the affinity (pKi 7.87) of this drug to α<sub>1L</sub>-AR in the canine aorta was lower than that (pKi 8.99) in the bovine prostate. These observations suggested that the pharmacological potencies of tamsulosin in the aorta and prostate may be different.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.