Human proximal and distal ureter tissues were studied to clarify whether the presence of mucosa affects contractile responses. In histological studies, human ureter was compared with urinary bladder (detrusor). Contractions in response to high KCl solution, phenylephrine, and carbachol were measured in intact and mucosa-denuded strips of human ureter. Tissue sections of human bladder and ureter were used for histological staining. Thirty-four percent of the ureter strips contracted spontaneously with highly variable patterns, and this was affected neither by mucosa nor by proximal or distal tissue origin. Upon stimulation with 40 mM KCl, ureter strips exhibited strong phasic and weak tonic contractions. In intact strips, normalized tonic force was lower than in denuded strips, but no consistent effect of mucosa was observed with phasic contractions. Absolute force values of phasic contractions were weaker in proximal than distal ureter strips, but similar when normalized to tissue wet weight. Stimulation with 80 mM KCl enhanced tonic contraction fourfold; phasic contractions occurred rarely. Phenylephrine produced no statistically significant stronger tonic contraction in distal compared with proximal ureter strips; nevertheless, in some strips, pre-existing spontaneous contractions increased. Carbachol did not influence ureter contractions. In the bladder, a suburothelial cell layer stained positive with α-smooth muscle actin (α-SMA)-specific antibodies could be further differentiated with vimentin- and desmin-specific antibodies. α-SMA positive cells were absent in suburothelial ureter tissue. Like in detrusor, the mucosa inhibits KCl-stimulated tonic ureter contractions. The mucosa of detrusor and ureter tissue exhibits distinct staining patterns for α-SMA, vimentin, and desmin. This suggests a different distribution of smooth muscle cells, fibroblasts, and myofibroblasts, which could be a target for pharmacological therapy of pathologic contractile processes.

Objectives: The mucosa of human detrusor strips impairs catecholamine-induced relaxation. In order to elucidate which signal transduction pathways are involved in this cross talk between the mucosa and detrusor, we have studied the effects of several pharmacological agonists and antagonists on noradrenaline-mediated relaxation in intact and mucosa-denuded detrusor strips. Patients and Methods: Strips of detrusor tissue were obtained from patients who had undergone cystectomy for bladder cancer and were set up for force measurement. KCl- or carbachol-precontracted strips were relaxed with increasing concentrations of noradrenaline in the absence and in the presence of nitric oxide synthase inhibitor, L-NAME; P2X-receptor antagonist, PPADS; ET_A-receptor antagonist, BQ-123; ET_B-receptor antagonist, BQ-788; cyclooxygenase inhibitor, diclofenac; AT₁-receptor antagonist, candesartan; and NK₁-receptor antagonist, L-703,606. Results: In intact strips, KCl-stimulated force was enhanced by all blockers; carbachol-stimulated force increased with L-703,606. In denuded strips, only L-NAME augmented the KCl-stimulated contraction. Noradrenaline relaxed the precontracted detrusor strips to a significantly larger extent and at lower concentrations in denuded than in intact strips. L-NAME, PPADS and BQ-123/BQ-788 had little effect on noradrenaline-induced relaxation, whereas diclofenac, candesartan and L-703,606 sensitized intact carbachol-stimulated detrusor strips to noradrenaline-induced relaxation. Conclusion: Inhibition of the noradrenaline-induced relaxation of precontracted human detrusor strips by the mucosa is attenuated by diclofenac, candesartan and L-703,606 suggesting the involvement of prostanoids, angiotensin and neurokinin pathways. Further experiments are required to unravel the exact mechanisms.