Stenken, Julie Ann2014-07-032014-07-031995-10-11https://hdl.handle.net/1808/14488This dissertation was digitized by the staff of the KU Libraries' Office of Scholarly Communication and Copyright.Microdialysis sampling has matured into a standard technique for sampling the rat brain in vivo. Microdialysis is beginning to be used for sampling from other tissues in laboratory animals. It has also been used in humans. The amount of material that enters or leaves a microdialysis probe is dependent upon many factors, some of which are presented in this dissertation. These factors include forced convection around the dialysis membrane, hindered diffusion through the membrane, and kinetic processes that occur in the tissue space. The aims of these studies were to identify factors that affect extraction efficiency in microdialysis systems and to develop develop methods to quantitate these factors. By setting up a specialized flow apparatus the effects of forced convection around a microdialysis membrane fiber were studied. From this same apparatus, values of the membrane permeability for hydroquinone, caffeine, theophylline, and theobromine were found for cuprophan, cellulose acetate and polyacrylonitrile membranes. A mathematical model was developed to determine the membrane permeability, and it fit the data well. The effects of inhibition of phenacetin and antipyrine metabolism in the liver and acetylcholine metabolism in the brain on the amount of each substance lost from the probe was studied. It was found through the development of a mechanistic model that micro vasculature exchange rates dominate metabolism rates in the liver. Inhibition of metabolism in the liver did not change the amount of material lost from the microdialysis probe during a local infusion. Acetylcholine is removed from the brain through only metabolic processes, thus inhibition affects the amount of material that is lost from the microdialysis probe after a local infusion of acetylcholine in the brain. A human study evaluated the usefulness of microdialysis for determining low levels of caffeine taken ad lib. This final study shows that microdialysis sampling although originally developed for brain studies in the rat, is finding more use in human studies.enDissertationopenAccess