The influence of barometric pressure changes upon membrane physiology and xenobiotic penetration

Whole body exposure changes in atmospheric pressure are common. For example, passengers on commercial air flights are exposed to a hypobaric pressure of approximately 170 mm Hg for the duration of the flight. Similarly activities such as deep sea diving and hyperbaric medicine, both of which are becoming more popular, can expose the body pressures of up to 6,000 mm Hg. Physiological changes in blood circulation and respiration under hyper and hypo baric pressures have been well documented, but the effects on xenobiotic entry into the body have not been systematically investigated. Whole body exposure to barometric pressure changes would be expected to have very different effects to local pressure changes induced by methods such as suction because the latter generates a pressure differential which could draw molecules across the barrier and has less profound effects on whole body physiology. The comparative effects of these two means of inducing barometric pressure changes to externally facing barriers such as the skin are at present unknown. The aim of this project is to determine the effects of whole body and local barometric pressure changes on membrane physiology and transmembrane chemical penetration. In oder to achieve this aim the project will: - Design and build a series of specialised cells that will allow the assessment of membrane physiology and penetration under both equilibrated and differential hyper and hypo baric conditions in vitro - Determine the effects of locally induced barometric changes upon membrane physiology and permeability using a complimentry range of transport models and analytical techniques - Mathematically model the process of barrier penetration using the in vitro data and design a series of in vivo tests. - Test whole body exposure changes to acute hyperbaric and hypobarric conditions, compare and contrast this data to the in vitro data and adapt the in silico model describing permeation It is anticipated that the data generated from this work can be used to assess both the toxicological exposure risk and potential to improve the delivery of therapeutic agents when applying barometric stress to biological membranes. Work Plan A systems biology approach to the design will be taken. The employment of a hierarchal series of membranes will allow mathematical modelling and descrition of barrier transport in multiple tissue types. Part 1 - 'In vitro assessment of barometric pressure changes on transport'. A specially designed jacket that can independently seal the donor and receiver compartment of a Franz cell will be designed and tested. A series of both porous and non porous synthetic membranes will be employed to investigate the influence of pressure on permeate diffusion and partition. Part 2 - 'Mathematical modelling'. The data sets generated in Part 1 will be fitted to the ideal behaviour expected from non-porous or porous membrane transport processes. A mathematical model to describing transmembrane transport in the absence of barrier changes under different barometric pressures will be developed and this will inform the study design for Part 3. Part 3 - 'Skin physiology and barrier changes'. The cells designed in Part 1 will be used to assess transmembrane penetration through full thickness skin. Pre and post pressure exposure transepidermal water loss, skin lipid packing, water permeability, coenocyte size and skin anatomy will be characterised using analytical techniques and structural changes correlated to barrier properties. The findings will be used to adapt and test the mathematical model generated in Part 2. Part 4 - 'In vivo assessment'. Whole animal protocols developed in previous work (Staff PhD student, 2010) but adapted to specalised hyper and hypobarric chambers will assess animal physiology, skin barrier properties and skin permeability under differential pressure condi