Characterization of Muscarinic Receptor Subtypes in Human Ureter

Background And Purpose: To date, the subtypes of muscarinic receptors in the human ureter have not been characterized. Recently, several clinical studies have suggested enhanced passage of ureteral stones after relaxation of the ureter using adrenergic antagonists. However, there is a paucity of information on ureteral receptors and their role in ureteral motility. The objective of our study was to evaluate whether all five of the known subtypes of muscarinic receptors are present in the human ureter and to determine the relative distribution of these subtypes.

Materials And Methods: Four ureters from human patients undergoing radical nephrectomy were paraffin tissue sectioned (5 microm) and applied to charged slides, deparaffinized, and hydrated. These sections underwent immunocytochemical (ICC) analysis of the density of each of the muscarinic receptor subtypes (M1-M5) with respect to the total area of ureteral tissue (I/A) present in every sample. Three ureters were harvested for reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of muscarinic receptor subtypes.

Results: All five receptor subtypes were present in the human ureter on ICC analysis. However, on RT-PCR analysis, only subtypes 2, 3, and 5 were present.

Conclusions: The results of our study demonstrate that muscarinic receptors are present in the human ureter. A novel finding is the identification of relatively high levels of M5 by both ICC and RT-PCR.