The present kinetic study of the permeability of rabbit erythrocytes has established that carrier systems are involved in the penetration of certain non-electrolytes. Saturation, competitive inhibition, and butanol inhibition kinetics were used to demonstrate the presence of carrier systems and the values of half-saturation constants (ø) were determined for the following water soluble non-electrolytes: glycerol, ethylene glycol, urea, and thiourea. These non-electrolytes are commonly used in permeability studies because they are relatively non-toxic and their small sizes allow penetration of the erythrocyte membrane within a reasonable length of time.

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To many investigators, these observations suggested the existence of a molecular “pump” mechanism responsible for the maintenance of the ionic gradients. Extensive research over the last twenty years has resulted in the assignment of this role to the magnesium-dependent, sodium- and potassium-stimulated adenosine triphosphatase, first reported by Skou in 1957. This membrane-bound enzyme is the subject of the research presented in this thesis.

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Transport properties of bovine intestinal brush border membranes were investigated. Isolation of brush border membrane vesicles involved magnesium precipitation followed by a sucrose density gradient. Characterization by alkaline phosphatase activity (the brush border marker enzyme) showed 7 fold enrichment over homogenate at the interface between 38 and 42% sucrose. This fraction was employed to study transport of sugars and amino acids. Transport of D-glucose into an osmotically active space, was sodium stimulated, and inhibited by phloridzin, D-galactose, and D-xylose. Transport of L-alanine was sodium stimulated and mediated by at least two systems. Apparent affinities for L-alanine transport were .039, and .943 mM. Maximum velocities were 29.2, and 53.4 pmoles/mg protein/sec, for the two systems. Transport of L-proline, L-lysine, L-methionine, and L-phenylalanine were sodium stimulated. Data indicated sodium independent transport accounted for more influx of L-lysine, L-methionine, and L-phenylalanine than sodium dependent transport. Sodium dependent and sodium independent fluxes were equal for uptake of L-proline. Amino acid inhibition data indicated a common transporter for methionine, alanine, and phenylalanine. There was an additional methionine transport system not shared by alanine or phenylalanine. None of the amino acids effectively inhibited methionine uptake. Data indicated praline was transported by system(s) not shared by the other amino acids. Bovine brush border membranes transported the amino acid analog alpha-methyl-aminoisobutyric acid by sodium stimulated processes. / Ph. D.

Peptide, plasma free, erythrocyte free and serum protein amino acid arteriovenous differences were quantified across the gastrointestinal tract (GIT) and liver of growing calves during a "steady state" and fasting metabolism. Six Holstein steer calves (136 kg) surgically equipped with cannulae in the aorta, portal vein and hepatic vein were maintained under constant light and fed a natural diet as 24 hourly meals per day. Blood was obtained simultaneously from all cannulae at 9 to 12 d postsurgery during the midpoint of a 1-hr feeding interval and following a 72-hr fast. Most amino acids were added to plasma by the GIT but fasting reduced the magnitude of this addition. GLN and GLU were the only plasma amino acids removed by the GIT. The liver removed a large portion of amino acids in portal plasma but a net splanchnic plasma free amino acid output occurred. Hepatic removal of amino acids, particularly VAL, ILE and LEU, increased after fasting. The GIT generally removed amino acids from the erythrocyte while the liver contributed amino acids to this pool. Peptide amino acids increased as blood crossed the GIT. Responses paralleled those of plasma free amino acids in direction but were threefold greater for peptide amino acids. A net output of peptide amino acids from the splanchnic bed was observed. Generally amino acids were added to the primarily globulin, albumin and mixed protein serum fractions while the pure albumin fraction contributed amino acids to the GIT. Fasting reversed the direction of response in the four fractions monitored. Arteriovenous differences for amino acids in two largely albumin fractions responded oppositely indicating a potential transport role of other proteins in these fractions. A more variable response was observed across the liver with direction and magnitude dependent upon individual amino acids. Fasting resulted in a release of amino acids by the liver into all four fractions. Several blood pools appear to be involved in the interorgan transport of amino acids. The extent and direction of transport varies with tissue, blood pool, nutritional status and amino acid. Quantitatively, peptides appear to be highly involved in interorgan movement of amino acids. / Ph. D.

Fung, Chun Kit. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 121-135). / Abstracts in English and Chinese. / Declaration --- p.i / Acknowledgement --- p.ii / Abbreviations --- p.iii / Abstract in English --- p.v / Abstract in Chinese --- p.vii / Table of Contents --- p.ix / List of Figures --- p.xii / Chapter Chapter 1 - --- Introduction / Chapter 1.1 --- Genus Cordyceps --- p.1 / Chapter 1.2 --- Cordyceps militaris --- p.4 / Chapter 1.3 --- Biological Functions and Chemical Constituents of Cordyceps militaris --- p.9 / Chapter 1.4 --- "Human Bronchial Epithelial Cell Line, 16HBE14o-" --- p.13 / Chapter 1.5 --- Ion Transport in Human Bronchial Epithelial Cells --- p.16 / Chapter 1.6 --- Objectives of the Experiments --- p.20 / Chapter Chapter 2 - --- Materials and Methods / Chapter 2.1 --- Solutions and Chemicals --- p.21 / Chapter 2.2 --- Preparation of Hot Water Cordyceps militaris Extract --- p.22 / Chapter 2.3 --- Culture of Cells --- p.23 / Chapter 2.4 --- Short-Circuit Current (lsc) Measurement --- p.24 / Chapter 2.5 --- Short-Circuit Current (lsc) Measurement in Nystatin-Permeabilized Monolayer --- p.29 / Chapter 2.6 --- Measurements of [Ca2+]i --- p.31 / Chapter 2.7 --- Measurement of PKA Activity --- p.36 / Chapter 2.8 --- Statistical Analysis --- p.37 / Chapter Chapter 3 - --- Results / Chapter 3.1 --- Regulation of Ion Transport in 16HBE14o- Cells by CM Water Extract --- p.38 / Chapter 3.1.1 --- Dose-Dependent Relationship of CM Water Extract --- p.39 / Chapter 3.1.2 --- "Involvement of CI"" Transport in CM-induced lsc Response" --- p.42 / Chapter 3.1.3 --- Involvement of K+ channels in CM-induced lsc Response --- p.47 / Chapter 3.1.4 --- Involvement of Adenylate Cyclase/cAMP/Protein Kinase A Pathway in CM-induced lsc Response --- p.52 / Chapter 3.1.5 --- Involvement of Ca2+-Dependent Pathway in CM-induced lsc Response --- p.57 / Chapter 3.1.6 --- "Effect of CM Extract on Apical CI"" Current and Basolateral K+ Current in Nystatin-Permeabilized Epithelia" --- p.61 / Chapter 3.1.7 --- Effect of CM Extract on PKA Activity --- p.67 / Chapter 3.2 --- Regulation of Ion Transport in 16HBE14o- Cells by Cordycepin --- p.70 / Chapter 3.2.1 --- Dose-Dependent Relationship of Cordycepin --- p.70 / Chapter 3.2.2 --- "Involvement of CI"" Transport in Cordycepin-induced lsc Response" --- p.73 / Chapter 3.2.3 --- Involvement of K+ channels in Cordycepin-induced lsc Response --- p.79 / Chapter 3.2.4 --- Involvement of Adenylate Cyclase/cAMP/Protein Kinase A Pathway in Cordycepin-induced lsc Response --- p.84 / Chapter 3.2.5 --- Involvement of Ca2+-Dependent Pathway in Cordycepin-induced lsc Response --- p.89 / Chapter 3.2.6 --- Effect of Cordycepin on Intracellular Ca2+ Concentrations --- p.93 / Chapter 3.2.7 --- "Effect of Cordycepin on Apical CI"" Current and Basolateral K+ Current in Nystatin-Permeabilized Epithelia" --- p.98 / Chapter 3.2.8 --- Effect of Cordycepin on PKA Activity --- p.104 / Chapter Chapter 4 - --- Discussion / Chapter 4.1 --- Regulation of Ion Transport in 16HBE14o- Cells by CM Extract --- p.107 / Chapter 4.2 --- Intracellular Signaling Mechanisms behind CM-induced lsc Responses --- p.110 / Chapter 4.3 --- Regulation of Ion Transport in 16HBE14o- Cells by Cordycepin --- p.111 / Chapter 4.4 --- Intracellular Signaling Mechanisms behind Cordycepin-induced lsc Responses --- p.114 / Chapter Chapter 5 - --- Conclusion / Chapter 5.1 --- Summary --- p.117 / Chapter 5.2 --- Future Directions --- p.120 / Chapter Chapter 6 - --- References --- p.121 / Chapter Chapter 7 - --- Publications --- p.136