ABSTRACT
BPA used in BNCT has a similar structure to some essential amino acids and is transported into tumor cells by amino acid transport systems. Previous study groups have tried various techniques of loading BPA to increase intracellular boron concentration. CHO-K1 cells demonstrate system L (LAT1) activity and are suitable for specifying the transport system of a neutral amino acid. In this study, we examined the intracellular accumulation of boron in CHO-K1 cells by amino acid transport control, which involves co-loading with L-type amino acid esters. Intracellular boron accumulation in CHO-K1 cells showed the greatest increased upon co-loading 1.0mM BPA, with 1.0mM l-Tyr-O-Et and incubating for 60min. This increase is caused by activation of a system L amino acid exchanger between BPA and l-Tyr. The amino acid esters are metabolized to amino acids by intracellular hydrolytic enzymes that increase the concentrations of intracellular amino acids and stimulate exchange transportation. We expect that this amino acid transport control will be useful for enhancing intracellular boron accumulation.
Subject(s)
Boron Compounds/pharmacokinetics , Boron Neutron Capture Therapy/methods , Drug Carriers/pharmacokinetics , Phenylalanine/analogs & derivatives , Tyrosine/pharmacokinetics , Amino Acid Transport Systems/pharmacokinetics , Animals , Boron Compounds/administration & dosage , Boron Compounds/chemistry , CHO Cells , Cricetinae , Cricetulus , Drug Carriers/administration & dosage , Drug Carriers/chemistry , Metabolic Clearance Rate , Phenylalanine/administration & dosage , Phenylalanine/chemistry , Phenylalanine/pharmacokinetics , Tyrosine/administration & dosage , Tyrosine/chemistryABSTRACT
[reaction: see text] Nine fluorescently labeled structurally varied polyguanidino dendrimers based on diamino acid monomeric units were individually synthesized in an efficient, scalable sequence using a trifluoroacetamide protecting group-perguanidinylation strategy. While the dendrimers varied significantly in their ability to enter a human lymphocyte cell line, the best transporters out-performed an oligoarginine reference standard.
Subject(s)
Amino Acid Transport Systems/chemical synthesis , Dendrimers/chemical synthesis , Fluorescent Dyes/chemical synthesis , Guanidine/chemistry , Polymers/chemical synthesis , Amino Acid Transport Systems/chemistry , Amino Acid Transport Systems/pharmacokinetics , Cell Line , Dendrimers/chemistry , Dendrimers/pharmacokinetics , Fluorescent Dyes/chemistry , Fluorescent Dyes/pharmacokinetics , Humans , Lymphocytes/drug effects , Lymphocytes/metabolism , Molecular Structure , Polymers/chemistry , Polymers/pharmacokinetics , Protein Transport/drug effectsABSTRACT
Mouse PAT1 (putative anion transporter, CEFX, slc26a6), an orthologue of human SLC26A6, was recently identified at the intestinal brush-border membrane and shown to transport organic anions such as formate and oxalate, as well as inorganic ions. In this study, we conducted functional characterization of the uptake of formate by HEK293 cells transfected with PAT1. The uptake of formate by PAT1 was increased in the presence of an outwardly-directed Cl gradient, whereas Na had no effect, and the uptake was independent of pH. The Km of PAT1 for formate was 3.75 mM. Various organic acids exhibited a cis-inhibitory effect on the uptake of formate by PAT1. Furthermore, the uptake was increased by preloading with -lactate, nicotinate, valproate and short-and medium-chain fatty acids, showing a trans-stimulatory effect. Thus, it was suggested that PAT1 transports organic acids as well as inorganic anions, demonstrating that it is involved in the intestinal absorption of anionic organic weak acids in the small intestine.
Subject(s)
Amino Acid Transport Systems/physiology , Antiporters/physiology , Organic Anion Transporters/physiology , Amino Acid Transport Systems/pharmacokinetics , Animals , Anion Transport Proteins , Antiporters/pharmacokinetics , Biological Transport, Active , Formates/metabolism , Intestinal Absorption , Mice , Oxalates/metabolism , Sulfate Transporters , SymportersABSTRACT
The permeability of dipeptide derivatives containing tryptophans and indole derivatives through Caco-2 cells was used as an in vitro intestinal absorption model in order to clarify structural factors which influence their intestinal epithelial permeation and metabolism. Most peptide derivatives were hydrolysed not only by the cytosolic enzymes in Caco-2 cells during permeation but also by enzymes released to the apical solution before cell permeation. The N-terminal blocked dipeptides were more resistant to hydrolases expressed in the Caco-2 cells and indole derivatives were not entirely degraded. Based on compound concentration dependency and comparison of permeability coefficients in apical-to-basolateral and basolateral-to-apical directions, the main absorption mechanism of compounds were determined. Compounds were then classified into three groups; (1) passively transported compounds, (2) actively transported compounds and (3) compounds excreted by P-glycoprotein.
