Effect of pH on weakly acidic and basic model drugs and determination of their ex vivo transdermal permeation routes

ABSTRACT The aim of the present study was to investigate the effect of donor pH on the transdermal permeability of the model drugs across rat skin and also to determine the major route of transport of the drugs. Weakly acidic drugs (partition coefficient) ibuprofen (3.6), aceclofenac (3.9), glipizide (1.9) and weakly basic drugs olanzapine (3.6), telmisartan (6.0), and sildenafil citrate (1.9) were selected for the study. The ex vivo permeation studies of these drugs at different donor pH (pH - 1.2, 4, 5, 6.8, 7.4, and 8) using Franz diffusion cell (area, 7.54 cm2) has shown a pH-dependent permeability. Among these drugs the weakly acidic drugs has shown higher permeation rates compared to the weakly basic drugs. The permeability coefficient and the distribution coefficient of the weakly basic drugs increased on increasing the pH whereas the weakly acidic drugs showed an inverse relation. The weakly basic drugs also showed an increase in permeation with increase in the fraction of unionized species indicating dominance of transcellular route of permeation. With an exception of sildenafil citrate, a weakly basic salt form of the drug which showed a high permeation value at pH 7.4 where 57% of the drug was unionized, indicating the involvement of both paracellular and transcellular route in its permeation.

Urinary cystine calculi and detection of polymorphism in the SLC3A1 gene in Sudanese children

To investigate polymorphism in exon 8 of the SLC3A1 gene in children with urinary cystine calculi in Khartoum. A semi-quantitative chemical method was used to analyse 175 urinary calculi removed surgically from paediatric patients at Soba Teaching Hospital in Khartoum between October 2005 and May 2009. DNA was extracted with phenol chloroform isoamyl alcohol, and exon 8 of the SLC3A1 gene was amplified in a thermocycler and sequenced with an AB3130 genetic autoanalyser. Of the 175 stones, 10 were cystine calculi [5.7%]. The sex ratio of the patients was 2.3:1 [boys to girls], and the mean age at cystine stone onset was 31.1 +/- 28.2 months [range, 3-125 months]. Of the 10 patients, 8 had a positive family history of calculi formation, 4 had bilateral calculi, 3 had both renal and urinary bladder calculi, and 2 had obstructive acute renal failure. All patients required more than one surgical operation. One patient had a missense mutation M467K in exon 8 of the SLC3A1 gene. The prevalence of cystine calculi among urinary calculi in Sudanese children was 5.7%. A family history was found in 80% of children. A mutation [M467T] was identified at exon 8 of the SLC3A1 gene in one child

Suppression of amino acid transporter LAT3 expression on proliferation of K562 cells / 华中科技大学学报（医学）（英德文版）

The activity of the mTOR pathway is frequently increased in acute myeloid leukemia, and is tightly related with cellular proliferation. Leucine is tightly linked to the mTOR pathway and can activate it, thereby stimulating cellular proliferation. LAT3 is a major transporter for leucine, and suppression of its expression can reduce cell proliferation. Here, we show that suppression of LAT3 expression can reduce proliferation of the acute leukemia cell line, K562. We investigated the mRNA and protein expression of LAT3 in several leukemia cell lines and normal peripheral blood mononuclear cells (PBMNCs) using RT-PCR and Western blotting. We also evaluated cell viability using a methyl thiazolyl tetrazolium (MTT) assay after blocking LAT3 expression with either shRNA targeted to LAT3 or a small molecular inhibitor BCH (2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid). LAT3 mRNA and protein expression was detected in leukemia cell lines, but not in normal PBMNCs. Using K562 cells, it was found that cellular proliferation and mTOR pathway activity were significantly reduced when LAT3 was blocked with either shRNA or BCH. Our results suggest that leukemia cell proliferation can be significantly suppressed by blocking LAT3. This finding may lead to a new strategy to develop clinical therapy for the treatment of acute myeloid leukemia.

Non-Type I Cystinuria Associated with Mental retardation and Ataxia in a Korean Boy with a New Missence Mutation(G173R) in the SLC7A9 Gene

Cystinuria is an inherited renal and intestinal disease characterized by defective amino acids reabsorption and cystine urolithiasis. It is unusually associated with neurologic symptoms. Mutations in two genes, SLC3A1 and SLC7A9, have been identified in cystinuric patients. This report presents a 13-yr-old boy with cystinuria who manifested difficulty in walking, ataxia, and mental retardation. Somatosensory evoked potential of posterior tibial nerve stimulation showed the central conduction dysfunction through the posterior column of spinal cord. He was diagnosed non-type I cystinuria by urinary amino acid analysis and oral cystine loading test. We screened him and his family for gene mutation by direct sequencing of SLC3A1 and SLC7A9 genes. In this patient, we identified new missence mutation G173R in SLC7A9 gene.

A case of Hyperornithinemia-Hyperam monemia-Homocitrullinuria Syndrome: a Patient Who Visited the Emergency Center with Mental Change

Rapid ammonia elevation in blood with accompanying mental change should be considered as a true medical emergency. In such a case, action leading to immediate diagnosis and the earliest possible treatment must occur in order to minimize permanent brain damage. Hyperornithinemia- Hyperammonemia-Homocitrullinuria (HHH) syndrome is a rare inborn errors of metabolism and autosomal recessive metabolic disorder caused by a deficiency of the mitochondrial ornithine transporter at the cellular level. Emergency physicians should take account of the possibility of HHH syndrome in patients with unreasonable hyperammonemia coupled with altered mental status. We report a case of a 59-year old man who presented with headache, nausea, vomiting and altered mental status. His serologic test showed hyperornithinemia, hyperammomemia, and homocitrullinuria. He was treated with fluid therapy and hemodialysis. His clinical manifestation improved and he was discharged after hemodialysis

Physiological, Pharmacological and Toxicological Implications of Heterodimeric Amino Acid Transporters

The heterodimeric amino acid transporter family is a subfamily of SLC7 solute transporter family which includes 14-transmembrane cationic amino acid transporters and 12-transmembrane heterodimeric amino acid transporters. The members of heterodimeric amino acid transporter family are linked via a disulfide bond to single membrane spanning glycoproteins such as 4F2hc (4F2 heavy chain) and rBAT (related to b0, +-amino acid transporter). Six members are associated with 4F2hc and one is linked to rBAT. Two additional members were identified as ones associated with unknown heavy chains. The members of heterodimeric amino acid transporter family exhibit diverse substrate selectivity and are expressed in variety of tissues. They play variety of physiological roles including epithelial transport of amino acids as well as the roles to provide cells in general with amino acids for cellular nutrition. The dysfunction or hyperfunction of the members of the heterodimeric amino acid transporter family are involved in some diseases and pathologic conditions. The genetic defects of the renal and intestinal transporters b0, +AT/BAT1 (b0, +-type amino acid transporter/b0, +-type amino acid transporter 1) and y+LAT1 (y+L-type amino acid transporter 1) result in the amino aciduria with sever clinical symptoms such as cystinuria and lysin uric protein intolerance, respectively. LAT1 is proposed to be involved in the progression of malignant tumor. xCT (x-C-type transporter) functions to protect cells against oxidative stress, while its over-function may be damaging neurons leading to the exacerbation of brain damage after brain ischemia. Because of broad substrate selectivity, system L transporters such as LAT1 transport amino acid-related compounds including L-Dopa and function as a drug transporter. System L also interacts with some environmental toxins with amino acid-related structure such as cysteine-conjugated methylmercury. Therefore, these transporter would be candidates for drug targets based on new therapeutic strategies.