A quantitative analysis of purinoceptor expression in the bladders of patients with symptomatic outlet obstruction

To compare the expression of the seven known P2X receptors in human bladder from male patients with detrusor instability caused by symptomatic bladder outlet obstruction with that from control bladders, using a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method.

Real-time quantitative RT-PCR provides a system for detecting and analysing RNA. Bladder biopsies were obtained from nine patients undergoing prostate surgery and control biopsies were obtained from eight age-matched men undergoing routine bladder endoscopy studies, and who were asymptomatic. Total RNA was extracted from each sample and 10 ng of this used for individual PCR reactions. The expression levels of the seven P2X genes in the total RNA were then determined.

In the control bladder, P2X1 was by far the predominant purinergic receptor at the RNA level, the remainder consistently present in the order P2X1 >> P2X4 > P2X2 > P2X7 > P2X5 >> P2X3 = P2X6 = 0. Calponin, a smooth muscle-specific protein, was used as a marker for smooth muscle content. In bladder from symptomatic patients, the P2X1/calponin ratio was greater than that in controls (P = 0.016). There appeared to be no difference in P2X2, but P2X4, P2X5, and P2X7 were all greater in the symptomatic bladder than in the controls, although these differences were not significant.

P2X1 is the predominant purinoceptor subtype in the human male bladder, consistent with pharmacological evidence. The amount of P2X1 receptor per smooth muscle cell is greater in the obstructed than in control bladder, suggesting an increase in purinergic function in the unstable bladder arising from bladder outlet obstruction.