Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, C84
Isolated perfused pig bladder: a novel experimental approach for the study of whole organ physiology in large animals
B. A. Parsons2, M. Drake2, B. Vahabi1,2
1. University of the West of England, Bristol, United Kingdom. 2. Bristol Urological Institute, Bristol, United Kingdom.
Our knowledge of bladder function remains incomplete and experimental approaches such as muscle strip experiments, though central to our current understanding, fail to reproduce the complex network of cell-cell interactions that underpin normal bladder function. Improving our understanding of bladder physiology necessitates the use of whole organ preparations and to date most of this work has been done using bladders from small rodents. Extrapolating findings generated using small laboratory animals to lower urinary tract physiology of large animals and to the clinical context is difficult, and requires careful validation. In order to overcome some of these limitations, the aim of this study was to develop an experimental model using an isolated whole pig bladder, which could be used to study the integrative physiology of the bladder. Pig bladders and their associated vasculature were retrieved from the abattoir, with a mean warm ischaemia time of 30±5 mins and a mean cold ischaemia time of up to 120±15 mins. A temperature-controlled organ bath with an integrated arterial pump-perfusion system was designed to preserve organ viability. The pig bladders were perfused with Krebs-bicarbonate buffer for a period of several hours and intravesical and intra-arterial pressures were monitored. Validation of tissue viability involved assessment of histology, arterial perfusion and pH. Cholinergic stimulation was undertaken by administration of carbachol (1µM-3mM) through either the vascular or intravesical route. Once perfused, the bladders remained viable on structural, perfusion and biochemical testing for a period of over 6 hours. Histologically, light microscopic examination of haematoxylin and eosin stained bladder biopsies taken after 6 hours of perfusion demonstrated well-preserved tissue architecture with no evidence of autolysis or necrosis. There was also no evidence of tissue ischaemia as no significant changes were recorded in the pH of the perfusate before and after its passage through the organ. Intravascular administration of carbachol elicited contractions of the pre-filled bladder (N=5) in a dose dependant manner with a maximum response of 98.8 ± 1.2 cmH2O and an EC50 of 96.7 ± 22.7 µM. Intravesical carbachol (300µM-3Mm) also elicited bladder contraction. Using a pump perfusion system, the viability of an isolated large animal bladder can be maintained for a prolonged period of time even after a limited period of warm and cold ischaemia. This experimental approach can be used to study whole organ function of large animal bladders, and the potential for different routes of drug administration may help discern the relative contribution of different cell types in tissue function.
Where applicable, experiments conform with Society ethical requirements