Distribution of alpha(1L)-adrenoceptors in canine prostate: Characterization by quantitative autoradiography

Our aim was to determine the distribution of alpha(1L)-adrenoceptors in can ine prostate by an autoradiographic technique using [H-3]JTH-601 (an alpha( 1L)-adrenoceptor antagonist) and [H-3]JTH-601-G1 (an active metabolite of J TH-601). Prostates were removed from three male beagle dogs. Several slices of the s pecimens were incubated with 5 nM of [H-3]JTH-601, [H-3]JTH-601-G1 and [H-3 ]tamsulosin (an alpha(1A)-adrenoceptor antagonist). For macroscopic autorad iography, visualization was performed using an imaging plate and image-anal yser. To examine microscopic localization of binding sites, preparations we re exposed, developed and fixed. Specific binding of [H-3]JTH-601 and [H-3]JTH-601-G1 was observed diffusely throughout the entire interstitium on macroscopic autoradiography. Specifi c binding of [H-3]tamsulosin was also recognized although the binding was w eaker than that of [H-3]JTH-601. On microscopic autoradiograms, the grains of each ligand were mainly distributed on smooth muscle. These results indicate morphologically that specific binding sites of JTH-B O1 and JTH-601-G1 exist in canine prostate, suggesting the distribution of alpha(1L)-adrenoceptors in this tissue, in addition to alpha(1A)-adrenocept ors.