INTRODUCTION: Bladder contractility in the transverse direction is often overlooked, because longitudinal strips are the regular tissues of choice in most contractility studies. In the present study, the effects of K+ channel blockers on transverse and longitudinal rat detrusor contractility were compared.
METHODS: Detrusor strips in transverse and longitudinal directions were dissected from young adult rats. Isometric tension was monitored using a myograph. The effects of tetraethylammonium chloride (TEA), 4-aminopyridine (4-AP), glibenclamide (Glib), iberiotoxin (IbTX), charybdotoxin (ChTX), and apamin on carbachol (CCh)-induced contractions were examined.
RESULTS: No contractile differences were present between transverse and longitudinal strips following CCh stimulation. Equal sensitivity to 4-AP and IbTX was detected in transverse and longitudinal strips. Pretreatment with Glib or ChTX resulted in greater suppression of CCh contractions in longitudinal strips. Although apamin suppressed contractions in both transverse and longitudinal strips, CCh potency was lower in transverse strips only.
CONCLUSION: Functional heterogeneity of transverse and longitudinal detrusor contractility was revealed from selective K+ channel blockade. Longitudinal strips were more susceptible to ATP-sensitive and intermediate-conductance Ca2+-activated K+ channel blockades, whereas transverse strips were affected more by blockade of small-conductance Ca2+-activated K+ channels. The potential importance in evaluating multidirectional contractility in pharmacologic studies of detrusor smooth muscle is reinstated.
Willmann Liang
KEYWORDS: K+ channel; Rat detrusor; Contraction; Transverse; Longitudinal
CORRESPONDENCE: Willmann Liang, PhD, School of Biological Sciences, Nanyang Technological University, Singapore 637551 ( ).
CITATION: Urotoday Int J. 2010 Apr;3(2).
doi: 10.3834/uij.1944-5784.2010.04.07