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Differential modulation by Ca 2+ ‐sensitive K + channels in longitudinal and transverse bladder strip contractions: implications in age‐related over‐active bladder symptoms
Author(s) -
Liang Willmann,
Lo Wan Ning
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1299-b
Subject(s) - contractility , myograph , carbachol , overactive bladder , endocrinology , urinary bladder , detrusor muscle , agonist , medicine , contraction (grammar) , urology , chemistry , pathology , receptor , stimulation , alternative medicine
Over‐active bladder (OAB) is affecting up to one‐third of middle‐aged adults worldwide. Physiological changes to the detrusor portion of the bladder are often associated with OAB symptoms. In the detrusor, smooth muscle cells (SMCs) are oriented both longitudinally and transversely. Evidence has pointed to the disparity in contractile responses between longitudinal SMCs (LSMCs) and transverse SMCs (TSMCs) in old adult rat bladders. The differences in contractility between LSMCs and TSMCs may also exist in young bladders, however only to be exacerbated during the aging process. Differences in the modulation of LSMC and TSMC contractility were hereby identified in the young adult rat detrusor. Detrusor strips of identical sizes were mounted on a myograph system where contractions were measured from SMCs in both orientations, i.e. LSMC‐ and TSMC‐oriented. A single application of the muscarinic agonist carbachol (CCh, 0.01‐50 micromol/L) yielded no differences in contractions between TSMC‐ and LSMC‐oriented strips. However, blockade of K Ca with tetraethylammonium (0.1–30 mmol/L) in TSMC‐oriented strips showed more prominent contractions than the LSMC‐oriented ones. The present findings indicated that young adult rat bladder strip contractions are modulated by K Ca to different extents, depending on the SMC orientation. It is of interests to determine which K Ca subtype(s) and if other types of K + channels contribute to the observed differential LSMC and TSMC contractility. The K + channel‐associated differences in LSMC and TSMC contractions may have implications in the initiation and progression of OAB accompanied with aging. Thus, future studies examining bladders from a wider age group of rats will provide more insights into the pathophysiology of OAB.