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Characterisation of the contractile dynamics of the resting ex vivo urinary bladder of the pig
Author(s) -
Lentle Roger G.,
Reynolds Gordon W.,
Janssen Patrick W.M.,
Hulls Corrin M.,
King Quinten M.,
Chambers John Paul
Publication year - 2015
Publication title -
bju international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.773
H-Index - 148
eISSN - 1464-410X
pISSN - 1464-4096
DOI - 10.1111/bju.13132
Subject(s) - trigone of urinary bladder , ex vivo , urinary system , urinary bladder , anatomy , in vivo , rhythm , contraction (grammar) , chemistry , urology , biology , medicine , microbiology and biotechnology
Objectives To characterise the area and movements of ongoing spontaneous localised contractions in the resting porcine urinary bladder and relate these to ambient intravesical pressure ( P ves ), to further our understanding of their genesis and role in accommodating incoming urine. Materials and Methods We used image analysis to quantify the areas and movements of discrete propagating patches of contraction ( PPC s) on the anterior, anterolateral and posterior surfaces of the urinary bladders of six pigs maintained ex vivo with small incremental increases in volume. We then correlated the magnitude of P ves and cyclic changes in P ves with parameters derived from spatiotemporal maps. Results Contractile movements in the resting bladder consisted only of PPC s that covered around a fifth of the surface of the bladder, commenced at various sites, and were of ≈6 s in duration. They propagated at around 6 mm/s, mainly across the anterior and lateral surface of the bladder by various, sometimes circular, routes in a quasi‐stable rhythm, and did not traverse the trigone. The frequencies of these rhythms were low (3.15 cycles/min) and broadly similar to those of cyclic changes in P ves (3.55 cycles/min). Each PPC was associated with a region of stretching (positive strain rate) and these events occurred in a background of more constant strain. The amplitudes of cycles in P ves and the areas undergoing PPC s increased after a sudden increase in P ves but the frequency of cycles of P ves and of origin of PPC s did not change. Peaks in P ves cycles occurred when PPC s were traversing the upper half of the bladder, which was more compliant. The velocity of propagation of PPC s was similar to that of transverse propagation of action potentials in bladder myocytes and significantly greater than that reported in interstitial cells. The size of PPC s, their frequency and their rate of propagation were not affected by intra‐arterial dosage with tetrodotoxin or lidocaine. Conclusions The origin and duration of PPC s influence both P ves and cyclic variation in P ves . Hence, propagating rather than stationary areas of contraction may contribute to overall tone and to variation in P ves . Spatiotemporal mapping of PPC s may contribute to our understanding of the generation of tone and the basis of clinical entities such as overactive bladder, painful bladder syndrome and detrusor overactivity.