Ureteral smooth muscle relaxation

Ureteral smooth muscle relaxation refers to the physiological reduction in the tone and peristaltic activity of the smooth muscle cells lining the ureteral wall. It is not a single molecular target but rather a therapeutic outcome mediated by various proteins, most notably the Alpha-1A and Alpha-1D adrenergic receptors, which are densely distributed in the distal ureter [1][2]. In clinical practice, achieving this relaxation is the primary goal of Medical Expulsive Therapy (MET), which is used to facilitate the passage of ureteral calculi (kidney stones) and alleviate the severe pain associated with renal colic [3][4]. By antagonizing alpha-adrenergic receptors or blocking calcium channels, drugs like tamsulosin or nifedipine decrease the resistance to stone movement, potentially avoiding the need for invasive surgical procedures [4]. The density of these receptors in the ureter makes them highly relevant for treating urolithiasis, though systemic side effects like hypotension can occur due to receptor presence in the vasculature [5]. Overall, modulating ureteral motility remains a cornerstone of conservative management for obstructive uropathy caused by small to medium-sized stones [3]. Sources: [1] Sigala S, et al. "Adrenoceptors in the human ureter." (2005) PubMed: 15758731. [2] StatPearls. "Alpha Blockers." (2023) NCBI: NBK553182. [3] American Urological Association (AUA). "Management of Ureteral Calculi Guidelines." [4] Campsen J, et al. "Medical expulsive therapy for ureteric stones." (2014) PubMed: 25132238. [5] Gravas S, et al. "Calcium channel blockers and the ureter." (2007) PubMed: 17395453.

Other names

Ureteral relaxationSpasmolysis of the ureterInhibition of ureteral peristalsisReduction of ureteral tone

Relaxation is primarily achieved through the antagonism of Alpha-1 adrenergic receptors (specifically Alpha-1A and Alpha-1D subtypes), which inhibits norepinephrine-mediated contraction of the ureteral smooth muscle [1][2]. Additionally, the inhibition of L-type voltage-gated calcium channels reduces the influx of extracellular calcium required for muscle contraction, while the activation of Beta-3 adrenergic receptors or inhibition of Phosphodiesterases (PDE) increases intracellular cAMP/cGMP levels to promote relaxation [3][5].