Thesis (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2006. / Embargoed. Vita. Bibliography: 191-192.

Our previous studies demonstrated that chronic social defeat (CSD) up-regulated expression of the serotonin transporter (SERT) and norepinephrine transporter (NET) in the brain, which was mediated by corticosteroid receptors. In the present study we first analyzed the alterations of corticosteroid receptors in different brain regions after the CSD paradigm. The results showed that CSD significantly reduced glucocorticoid receptor (GR) protein levels in the CA1 and dentate gyrus of the hippocampus, as well as in central and basolateral nuclei of the amygdala, which was accompanied by the translocation of GR from cytoplasm to nuclei. CSD also markedly reduced GR mRNA levels and MR immunoreactivity in the CA1, CA3 and dentate gyrus areas of the hippocampus. Conversely, CSD pronouncedly enhanced GR mRNA and protein levels in the dorsal raphe nucleus and locus coeruleus relative to the control. As an extension of our previous studies, in situ hybridization and immunohistochemical staining demonstrated that CSD regimen caused a notable increase of SERT mRNA levels in the dorsal raphe nucleus and increased SERT immunoreactivities in CA1 and CA3 of the hippocampus, as well as those in the basolateral nuclei of the amygdala. Likewise, CSD regimen resulted in an evident enhancement of NET immunoreactivity in the CA1 of the hippocampus and in the basolateral nuclei of the amygdala. Our current findings suggest that GR expressional alterations in response to CSD are complex and brain region-specific, which may correspond to their different functions in these regions.

No description available.

The current project examined the ability of nicotine to modulate dopamine transporter (DAT) function. Initial experiments determined the dose-response for nicotine to modulate dopamine (DA) clearance in rat striatum and medial prefrontal cortex (MPFC) using in vivo voltammetry and determined if this effect was mediated by nicotinic receptors (nAChRs). In both striatum and MPFC, nicotine increased DA clearance in a mecamylamine-sensitive manner, indicating nAChR-mediation. The effect of acute nornicotine on DAT function was also determined. In contrast to nicotine, nornicotine in a dose-related manner decreased striatal DA clearance in a mecamylamine-sensitive manner, indicating nAChR mediation. To determine if tolerance developed to the nicotine effect nicotine, separate groups of rats were injected once daily for 5 days with nicotine or saline. DA clearance in striatum and MPFC was determined 24 hrs after the last injection. Nicotine increased DA clearance only 10-15% in the group repeatedly administered nicotine, demonstrating that tolerance developed. To determine if nicotine altered striatal DAT efficiency, following nicotine injection, DAT density and maximal velocity of [3H]DA uptake was determined using [3H]GBR12935 binding and saturation analysis of [3H]DA uptake in rat striatum, respectively. Nicotine did not alter the Bmax or Kd of maximal binding of [3H]GBR12935 binding. However, an increase in Vmax was observed at 10 and 40 min following nicotine injection, suggesting that nicotine increases DAT efficiency. To determine if systemic nicotine enhanced DAT function via an action at nAChRs on striatal DA terminals, [3H]DA uptake was determined in striatum in vitro in the absence or presence of nicotine in the buffer. Nicotine did not alter the Vmax for [3H]DA uptake in vitro, suggesting that the nicotine-induced increase in DAT function observed in vivo is mediated by nAChRs on DA cell bodies or another site which indirectly alters DAT function. To determine if the increase in DAT efficiency was due to increased surface expression of striatal DAT, biotinylation and Western blot analyses were performed. Nicotine did not alter striatal DAT, suggesting that the nicotine-induced increase in DA clearance in vivo and DAT efficiency in vitro is not the result of increased trafficking of this protein to the cell surface.

The development of fatigue has been an area of interest to athletes and scientists alike for many years. Often, particularly during prolonged exercise in the heat, there is no obvious peripheral reason for fatigue and the central nervous system is cited as the source. The mechanisms and potential manipulations of this fatigue remain largely unclear. Chapters Three and Four attempted to reduce the transport of the serotonin precursor tryptophan into the brain in order to reduce or delay serotonin synthesis and therefore increase exercise capacity. In Chapter Three branched-chain amino acid drinks were fed before and during prolonged cycling to exhaustion in the heat on two occasions and control drinks were fed on two other occasions. There was no effect of the branched-chain amino acids on exercise capacity and the intra-individual variability in seven of the eight participants was small. One participant did appear to cycle for longer on the branched-chain amino acid trials compared to the control trials. In Chapter Four a 104 g bolus of amino acids, designed to deplete plasma tryptophan concentration, was fed seven hours before a prolonged cycle to exhaustion in the heat. There was no difference in exercise capacity between the tryptophan depletion trial and the control trial in which tryptophan was also ingested. These findings suggest that the delivery of tryptophan to the central nervous system is not the only factor influencing the onset of fatigue. The investigation undertaken in Chapter Five looked at the serotonin transporter density on the blood platelets of current and retired international level athletes competing in either endurance or sprint running events and a sedentary control group. Using the platelet as an accessible and reliable model for the serotonergic neuron, the maximum number of binding sites was assessed using the radio-labelled serotonin reuptake inhibitor [3H]Paroxetine. Those currently training for endurance events had a greater number of binding sites than any of the other groups. This supports previous findings and suggests that endurance training can increase the number of serotonin transporters on blood platelet membranes. During resting heat exposure in Chapter Six, the application of a 1 % menthol solution to the skin of the forearms, back and forehead elicited a warming sensation in some individuals and a cooling sensation in other individuals, but never any change in skin or core temperature nor skin blood flow. A small proportion of individuals did not perceive any change in skin thermal sensation. Chapter Seven applied these findings to a pre-loaded twenty minute exercise performance test in the heat. It was hypothesised that those who perceived a warming effect may perform worse when a menthol solution was applied compared to a control solution and conversely, those who perceived a cooling sensation may perform better with a menthol solution than with a control solution. There was no difference in exercise performance between those who felt a warming sensation and those who felt a cooling sensation. Those who felt a warming sensation felt significantly warmer on the menthol trial than the control trial but this did not affect their performance. However, those who reported a cooling sensation tended to feel cooler on the menthol trial than the control trial, and there was a tendency for an improvement in performance on the menthol trial compared to the control trial. Due to the experimental protocols adopted in this thesis it was possible to assess the reliability of an exercise capacity test compared to an exercise performance test. Chapter Three showed a coefficient of variation of 11.0 ± 11.2 % and Chapter Four showed a 11.5 ± 12.4 % variability for exercise capacity tests. Chapter Seven showed a coefficient of variation in a pre-loaded time-trial exercise performance test of 3.9 ± 9.6 % suggesting that an exercise performance test may be more reliable than an exercise capacity test. However, the aims of an investigation are still likely to be the main factor influencing the choice of protocol. It seems likely that no single mechanism will be responsible for the cessation of exercise. The investigations undertaken in this thesis also highlight many avenues for future exploration.

Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology & Toxicology Student: Patrícia Čečková Supervisor: PharmDr. Ivan Vokřál, Ph.D. Title of diploma thesis: Study of drug interactions with OATP family transporters using intestinal tissue slices An essential role in the action of orally administered drugs is their absorption through the intestinal barrier. It expresses a variety of transporters, including the OATP2B1 and OATP1A2 influx transporters, belonging to the SLC family. They are located on the apical membrane of enterocytes and allow the flow of endogenous and exogenous substances from the lumen of the intestines to the enterocyte. They affect not only the pharmacokinetics of drugs, but also their safety and efficacy. They represent sites of drug interactions with other drugs/food components that may altered drug efficacy or toxicity. Since FDA (The Food and Drug Administration) and EMA (European Medicines Agency) do not have intestinal OATP transporters included in their guidelines for preclinical studies, there is no single model of interaction study. The limitations of cell models and genetically modified organisms lead to the development of new methods such as the ex vivo method of precision cut intestinal slices (PCIS), which represents a tissue model...

Introdução: Doenças cardiovasculares constituem importante causa de morte em todo mundo e a hipercolesterolemia está diretamente relacionada como fator agravante desta morbidade. A dieta desempenha papel importante neste processo e alguns alimentos como o amaranto, especialmente sua proteína, tem mostrado capacidade de redução do colesterol plasmático. Estudos sugerem que este efeito está relacionado a peptídeos formados durante a digestão da sua proteína, os quais desempenham um papel importante na regulação e modulação do metabolismo lipídico. Os efeitos hipocolesterolêmicos, já observados, indicam o uso da proteína do amaranto como um composto bioativo direcionado para a promoção da saúde. Considerando que os efeitos hipocolesterolêmicos destes peptídeos são complexos e há diversas hipóteses formuladas, torna-se importante a realização de estudos visando avaliar a interação dos peptídeos na absorção intestinal do colesterol e da sua modulação genética. Objetivos: Verificar os efeitos do hidrolisado da farinha do grão de amaranto na absorção de colesterol e modulação de genes ABCA1, ABCG1, NPC1L1, AMPK, HMGR e SREBP-2em células Caco-2, e modulação dos genes ABCG8, HMGR, SREBP-2 e AMPKem enterócitos de hamsters. Metodologia: O amaranto foi triturado, sua farinha desengordurada e sua proteína isolada, com posterior digestão in vitro e filtração dos peptídeos. Três experimentos in vitro foram conduzidos com as células: permeação de hidrolisado, permeação de colesterol e de efeito sob a expressão gênica. No primeiro, o hidrolisado proteico de amaranto foi permeado em culturas celulares de Caco-2 no tempo de 2 horas. O permeato foi coletado e analisado por LC/MS/MS. No segundo, o hidrolisado de amaranto foi incorporado a micelas de colesterol e incubados em culturas celulares, nas concentrações de 1,0 mg/ml, e 3,0 mg/ml em tempos de 2h. Também em concentrações de 3,0 mg/ml foi adicionado albumina e caseína para efeito comparativo. O conteúdo de colesterol na porção apical e basolateral foi analisado em HPLC. O terceiro experimento foi avaliaçãoda exposição do hidrolisado, em concentrações de 0,5 mg/ml, 1,0 mg/ml e 3,0 mg/ml, em tempos de 2h e 12h. Após este período, foi realizada a extração de RNA total, avaliação de rendimento e integridade do material; medida quantitativa de expressão de RNAm por RT-PCR e quantificação relativa da expressão por ?CT dos genes ABCA1, ABCG1, ABCG8, NPC1L1, AMP1, HMGR e SREBP-2das células Caco-2 e tecido intestinal de hamsters, coletados em ensaios anteriores. Resultados: Na permeação de colesterol não houve diferença entre as concentrações dos hidrolisados proteicos e controle, porém o hidrolisado de amaranto em 1,0 mg/ml demonstrou uma tendência em diminuir a absorção de colesterol (p = 0,05). Na exposição das células Caco-2 aos peptídeos por 2h, houve uma diminuição nas concentrações de RNAm dos genes ABCA1, NPC1L1, AMPK, HMGR e SREBP-2 nas concentrações de 3,0 mg/ml. O tempo de exposição de 12h apresentou resultados semelhantes ao tempo de 2h. Somente a expressão gênica de ABCG8foi influenciada pelo isolado proteico de amaranto no experimento in vivo. Conclusão: A partir do exposto, podemos concluir que os peptídeos do grão de amaranto influenciam o metabolismo de colesterol por mecanismos genéticos. Portanto, torna-se uma alternativa a ser introduzida na dieta de indivíduos saudáveis e em pacientes com hipercolesterolemia, visando a prevenção de agravos e como estratégia de terapia adicional no controle dos níveis de LDL-c plasmático. Contudo, mais experimentos in vivo e em humanos são necessários para estabelecer a dose efetiva para consumo. / Introduction: Cardiovascular diseases are an important cause of death worldwide and hypercholesterolemia is directly related as an aggravating factor of this morbidity. Diet plays an important role in this process and some foods such as amaranth, especially its protein, have shown ability to lower plasma cholesterol. Studies suggest that this effect is related to peptides formed during the digestion of their protein, which play an important role in the regulation and modulation of lipid metabolism. The hypocholesterolemic effects, already observed, indicate the use of amaranth protein as a bioactive compound aimed to promoting health. Considering that the hypocholesterolemic effects of these peptides are complex and there are several hypotheses formulated, it is important to carry out studies to evaluate the interaction of peptides in the intestinal absorption of cholesterol and its genetic modulation. Objectives: To verify the effects of amaranth grain flour hydrolyzate on cholesterol uptake and ABCA1, ABCG1, NPC1L1, AMPK, HMGR and SREBP-2 genes modulation in Caco-2 intestinal cells, and modulation of ABCG8, HMGR, SREBP-2 genes and AMPK in hamster intestinal cells. Methodology: Amaranth was crushed, the created flour was defatted and its protein isolated, with subsequent in vitro digestion and filtration of the peptides. Three in vitro experiments were conducted with the cells: hydrolyzate permeation, cholesterol permeation and genetic expression. In the first, the amaranth protein hydrolyzate was permeated in Caco-2 cell cultures in the time of 2 hours. The permeate was collected and analyzed by LC/MS/MS. In the second, the amaranth hydrolyzate was incorporated into cholesterol micelles and incubated in cell cultures at concentrations of 1.0 mg/ml and 3.0 mg/ml in times of 2 h. Also, at concentrations of 3.0 mg/ml albumin and casein were added for comparison. Cholesterol content in the apical and basolateral portion was analyzed by HPLC. The third experiment was to evaluate the exposure of the hydrolyzate at concentrations of 0.5 mg/ml, 1.0 mg/ml and 3.0 mg/ml, in times of 2 h and 12 h. After this period, the extraction of total RNA, evaluation of yield and integrity of the material was performed; quantitative measurement of mRNA expression by RT-PCR and relative quantification of ?CT expression of the ABCA1, ABCG1, ABCG8, NPC111, AMPK, HMGR and SREBP-2 genes from Caco-2 cells and hamster intestinal tissue, collected in previous assays, were finalized. Results: In cholesterol permeation there was no difference between the concentrations of the protein hydrolysates and control, but the amaranth hydrolyzate at 1.0 mg/ml showed a tendency to decrease the cholesterol absorption (p = 0.05). Exposure of Caco-2 cells to peptides for 2 h resulted in a decrease in ABCA1, NPC111, AMPK, HMGR and SREBP-2 mRNA levels at concentrations of 3.0 mg/ml. The exposure time of 12h presented results similar to the time of 2h. Only the gene expression of ABCG8 was influenced by the amaranth protein isolate in the in vivo experiment. Conclusion: From the above, we can conclude that amaranth peptides influence the metabolism of cholesterol by genetic mechanisms. Therefore, it becomes an alternative to be introduced in the diet of healthy individuals and in patients with hypercholesterolemia, aiming at the prevention of aggravations and as a strategy of additional therapy in the control of plasma LDL-c levels. However, more studies should bedone with animals and humans to define the dose-efficiency for diet.

The rapid emergence of multidrug resistant bacterial strains represents a major global healthcare issue. Amongst five known classes of membrane transporters, which play a huge role in multidrug efflux, primary-active ATP-binding cassette (ABC) transporters are ATP powered whilst secondary-active transporters utilize electrochemical ion gradients to drive substrate transport. Mechanistic insights into transport by these proteins can help with the design and development of novel therapeutic agents against multidrug resistance, and can increase our understanding of the physiological functions of these transporters. Although available crystal structures illustrate a common alternate access model for transport by ABC transporters, the mechanisms by which metabolic energy is coupled to the transport cycle is still elusive. This thesis presents a series of functional studies using whole cells as well as artificial phospholipid membranes to study the energetics of transport, and the influence of membrane phospholipids on substrate transport by the homodimeric Escherichia coli lipid A/multidrug ABC exporter MsbA. Current alternating access models for ABC exporters involve cycling between conformations with inward- and outward-facing substrate-binding sites in membrane domains (MDs) in response to engagement and hydrolysis of ATP at the nucleotide-binding domains (NBDs). Here we report that MsbA also utilizes another major energy currency in the cell by coupling substrate transport to a transmembrane electrochemical proton gradient. In this thesis, analogous substrate transport reactions are also studied for two other ABC exporters, the MsbA homologue LmrA and the human multidrug transporter ABCG2. The dependence of ATP-dependent transport on proton coupling, and the stimulation of MsbA-ATPase by the chemical proton gradient highlight the functional integration of both forms of metabolic energy. It also raises questions about the role of NBDs in the transport process. Comparisons of drug transport and resistance in cells expressing MsbA-MD (truncated MsbA lacking the NBD) and full length MsbA (MsbA-WT) demonstrate increased transport efficiency of MsbA-WT compared to MsbA-MD. In addition, growth studies using E. coli WD2 cells, which are conditionally defective in MsbA’s essential activity in lipid A transport, show that lipid A transport can be restored by the expression of MsbA-WT but not MsbA-MD or ATP-hydrolysis impaired Walker A mutant (MsbA- ΔK382). Lastly, we also present biochemical experiments with proteoliposomes with a defined phospholipid composition, which suggest that cardiolipin is essential for the transport activity of MsbA. These techniques open the way to further explore lipid-proteins interactions and examine the physiological role(s) of MsbA. In conclusion, this thesis produces new insights in the mechanisms of transport and energy coupling in ABC exporters.

Objetivos: O objetivo deste trabalho foi desenvolver modelo farmacocinético (popPK) populacional para descrever simultaneamente as concentrações das fluoroquinolonas (levofloxacino – LEV e ciprofloxacino – CIP) no plasma, pulmão e próstata na presença e ausência do inibidor da P-gp tariquidar (TAR) visando determinar a contribuição desse transportador de efluxo na distribuição tecidual desses antimicrobianos. Método: Para alcançar este objetivo as seguintes etapas foram realizadas: i) foi validado o método analítico de HPLC-fluorescência para quantificação de CIP em amostras de plasma e microdialisado; ii) foram estabelecidas as condições para microdiálise para o CIP e as taxas de recuperação in vitro, por diálise e retrodiálise, e em tecido pulmonar e prostático in vivo por retrodiálise; iii) foi avaliada a farmacocinética do LEV após administração a ratos Wistar via i.v. bolus e por nebulização intratraqueal na dose de 7mg/kg na ausência e após administração prévia de TAR (15 mg/Kg i.v.); iv) foi desenvolvido um modelo popPK para prever as concentrações do LEV simultaneamente no plasma, pulmão e próstata após administração intravenosa e intratraqueal na presença e ausência do TAR; v) foi desenvolvido o modelo popPK para descrever as concentrações de CIP simultaneamente no plasma, pulmão e próstata após administração a ratos Wistar da dose de 7 mg/kg i.v. bolus na presença e ausência de TAR (15 mg/kg i.v.); vi) Para ambos os fármacos os dados foram avaliados por análise não-compartimental e modelados por modelo de quatro compartimentos modificado, com ajuda do software NONMEN®. Resultados e Conclusões. i) Método analítico foi desenvolvido e validado com sucesso para quantificação de CIP em HPLC/fluorescência mostrando-se linear na faixa de 10–2000 ng/mL em plasma e 5–1000 ng/mL em microdialisado com coeficientes de determinação (r2) superiores a 0,99. Os valores obtidos de erro padrão relativo para ensaios de precisão intra e inter-dia foram entre 8,8 e 6,0 %, para microdialisado entre 11,1 e 7,4 % para plasma, respectivamente. Os valores de exatidão foram 86,1% entre 114.3% para microdialisado e 85,6% entre 108,2% para plasma; ii) A avaliação do CIP por microdiálise mostrou recuperação concentração independente (0,25 - 1,5 μg/mL). Além disso, não houve diferença entre as recuperações obtidas por diálise e retrodiálise para o mesmo fluxo. No fluxo selecionado para os experimentos (1,5 μL/min) as recuperações médias por diálise e retrodiálise foram 23,0 ± 2,8% e 22,8 ± 1,6 %, respectivamente. A recuperação relativa das sondas in vivo foi de 11,3 ± 1,9 e 13,1 ± 2,7 % para pulmão e próstata, respectivamente; iii) A análise dos perfis plasmáticos e teciduais LEV após dose intravenosa do grupo controle (sem TAR) mostrou boa penetração tecidual na próstata (ƒT = 0,68) e no pulmão (ƒT = 0,69). Para a mesma via de administração, o grupo TAR mostrou uma penetração praticamente inalterada para o pulmão (ƒT = 0,81) e um aumento de mais de 2 vezes na penetração prostática (ƒT= 1,64). Na dose intratraqueal houve um aumento significativo na biodisponibilidade para o grupo TAR (F = 0,86) em relação ao controle (F = 0,4). Nessa via de administração foi detectado um aumento significativo na exposição (ASC) do pulmão ao LEV no grupo TAR demonstrando que o transporte por efluxo no pulmão é mais relevante quando o fármaco é administrado pela via intratraqueal; iv) Para o LEV, o modelo popPK de quatro compartimentos foi capaz de descrever simultaneamente os dados no plasma, pulmão e próstata na presença e ausência do TAR. Além disso, o modelo para administração intravenosa foi estendido e adaptado para administração intratraqueal. Foi possível analisar o impacto do transporte por efluxo sobre a penetração tecidual do LEV por diferentes vias de administração utilizando o modelo popPK; v) A avaliação do perfil farmacocinético plasmático do CIP após administração intravenosa, na presença e ausência de TAR, demonstrou diferença significativa entre todos os parâmetros calculados por análise não-compartimental, exceto para a constante de velocidade de eliminação (= 0,05). Em relação à penetração tecidual do CIP na próstata e pulmão, não houve alteração significativa nos parâmetros de eliminação e exposição tecidual do fármaco na presença do inibidor de efluxo TAR ( = 0,05), demonstrando que o transporte por efluxo possui papel minoritário no processo de distribuição do fármaco para os tecidos estudados. O modelo popPK de quatro compartimentos foi capaz de descrever as concentrações plasmáticas totais, livres no pulmão e próstata em presença e ausência de TAR, simultaneamente; vi) O modelo popPK desenvolvido permitiu o estudo mais profundo do processo de distribuição do LEV e do CIP no pulmão e próstata. / Objectives: The aim of this study was to develop a population pharmacokinetic model (popPK) able to simultaneously describe fluoroquinolones (levofloxacin – LEV and ciprofloxacin – CIP) concentrations in plasma, lung and prostate in the presence and absence of the inhibitor of P-gp tariquidar (TAR) to determine the contribution of this efflux transporter on the tissue distribution of these antimicrobials. Methods: To achieve this goal the following steps were taken: i) An analytical method by HPLC-fluorescence was developed and validated for CIP analysis in plasma and microdialysate samples; ii) microdialysis conditions were established for CIP including determination of in vitro relative recovery by dialysis and retrodialysis. The relative recovery was also determined in vivo, in lung and prostate, by retrodialysis; iii) LEV pharmacokinetics was evaluated after intravenous (i.v.) bolus and intratracheal (i.t.) administration of 7 mg/kg dose alone and following TAR administration (15 mg/kg i.v.) to Wistar rats; iv) a popPK model was developed to describe and predict LEV concentrations in plasma, lung and prostate following i.v. and i.t. dosing with and without TAR co-administration; v) the popPK model developed was used to describe CIP concentrations in plasma, lung and prostate after i.v. bolus administration of 7 mg/kg in presence and absence of TAR; vi) For both drugs non-compartmental analysis was performed besides data modeling by four compartment model using NONMEN®. Results and Conclusions i) The analytical method was developed and successfully validated for quantification of CIP by HPLC/fluorescence. The method was linear in the range of 10-2000 ng/mL in plasma and 5-1000 ng/mL in tissues microdialysate samples with coefficients of determination (r2) higher than 0.99. The relative standard error (RSD) obtained for intra and inter-day precision were lower than 8.8% and 6.0% for microdialysate and lower than 11.1 and 7.4% for plasma, respectively. The accuracy was 86.1% to 114.3% for microdialysate and 85.6 to 108.2 % for plasma samples; ii) the evaluation of CIP microdialysis probes relative recovery in vitro showed that the recovery was concentration independent (0.25 to 1.5 μg/mL). In addition, there was no statistical difference between the recoveries determined by dialysis and retrodialysis at the same flow rate. Using the selected flow rate (1.5 μL/min) the recoveries by dialysis and retrodialysis were 23.0 ± 2.8% and 22.8 ± 1.6%, respectively. CIP relative recoveries in vivo by retrodialysis were 11.3 ± 1.9 and 13.1 ± 2.7% for lung and prostate, respectively; iii) the analysis of LEV plasma and tissues concentration-time profiles after i.v. dosing showed a good tissue penetration of LEV in the prostate (ƒT = 0.68) and lung (ƒT = 0.69). For the same route of administration, TAR group showed virtually the same penetration into lung (ƒT = 0.81) and an increase of over 2 fold in drug levels in prostate (ƒT = 1.64). For the i.t. dose, there was a significant increase on LEV bioavailability for TAR group (F = 0.86) compared to control (F = 0.4). Furthermore, a significant increase was detected on lung exposure to LEV for TAR group indicating that efflux transport in the lung is more relevant when the drug is administered by the i.t. route; iv) For LEV, a four compartment model was able to describe the data simultaneously in plasma, lung and prostate in the presence and absence of TAR. Moreover, the intravenous model was extended to adapt the intratracheal dosing route. The popPK model allowed to analyze the impact of efflux transport on tissue LEV penetration of different routes of administration; v) the evaluation of plasma CIP profiles after i.v. dosing with and without TAR showed a significant difference in all parameters determined by non-compartmental analysis in the TAR group, except the elimination rate constant (α = 0.05). The CIP tissue penetration in prostate and lung, no significant difference was observed in tissues exposure and elimination rate when TAR was present demonstrating that efflux transporter play a minor role on CIP distribution to tissues investigated (α = 0.05). The popPK model with four compartments was able to describe CIP concentrations in plasma, lung and prostate in the presence and absence of TAR, simultaneously; vi) the popPK model developed allowed a more detailed investigation of LEV and CIP distribution process in lung and prostate.

by Wen-Liang Zhou. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (p. 125-144). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.