Evidence for the presence of alpha(1) adrenoceptor subtypes in the human ureter

Several studies have proposed a role for alpha(1) adrenoceptors (ARs) in ureteral physiology, indicating that they are present in the ureter; however, few studies have been done to identify alpha(1) AR subtypes present in this area. Thus, this study was carried out to characterize the alpha(1) AR subtype gene and protein expression in proximal, medial, and distal region of the human ureter. Methods: Molecular characterization of alpha(1) AR subtypes were analyzed by semi-quantitative RT-PCR. alpha(1) AR protein expression was studied by saturation binding curves and by competition binding curves with selective antagonists. Analysis of data was performed using the GraphPad PRISM 4 software. Results: Analysis of saturation binding curves revealed a heterogeneous distribution of alpha(1) AR binding sites, the B-max for the distal ureter was indeed 52.5 +/- 5.4 fmol/mg prot, while a lower similar density of alpha(1) ARs was demonstrated in the medial (25.2 +/- 1.7 fmol/mg prot) and proximal (23.4 +/- 0.4 fmol/mg prot) ureters. Molecular and pharmacological characterization of alpha(1) AR subtypes indicated that each receptor was present, although with differences in terms of the amount expressed. Conclusions: Human ureter was endowed with each alpha(1) AR subtype, although alpha(1D) and alpha(1A) ARs were prevalent over alpha(1B) ARs. Radioligand binding results revealed that there were no significant differences in the K-d between ureteral regions, while a heterogeneous distribution of alpha(1) AR binding sites was detected, with the highest density of alpha(1) ARs in the distal ureter and a lower similar density in the medial and proximal ureters. (C) 2004 Wiley-Liss, Inc.