inhibitor, 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH). The affinity of [14C]L-leucine uptake and the inhibition profiles of [14C]L-leucine uptake by various amino acids in the Saos2 cells were comparable with those for the LAT1 expressed in Xenopus oocytes. The majority of [14C]Lleucine uptake is, therefore, mediated by LAT1 in the Saos2 cells. These results suggest that the transports of neutral amino acids including several essential amino acids into Saos2 human osteogenic sarcoma cells are for the most part mediated by LAT1. Therefore, the Saos2 human osteogenic sarcoma cells are excellent tools for examine the properties of LAT1. Moreover, the specific inhibition of LAT1 in tumor cells might be a new rationale for anti-tumor therapy.
Amino Acid Transport System L* ; Amino Acids ; Amino Acids, Essential ; Amino Acids, Neutral ; Humans* ; Oocytes ; Osteosarcoma* ; Xenopus

The continuous growth and proliferation of cells are essential for the wound healing process, and the amino acid transporters plays an important role in the continuous growing and proliferating cells. Among the amino acid transport systems, the amino acid transport system L, which is a Na+/-independent neutral amino acid transport system, is a major route for providing living cells including tumor cells with neutral amino acids including several essential amino acids. In the present study, to elucidate the role of amino acid transport system L in the wound healing process, we investigated the expression pattern of LAT1 and LAT2 in the healing process after inflicting the wound on skin of rat. The expression of LAT1 was increased at 12 hours after inflicting the wound and was similar to the control group getting closer to 7 days. The expression of LAT2 was increased at 1 day and 3 days after inflicting the wound and was similar to the control group getting closer to 7 days. These results suggest that the LAT1 and LAT2 play important roles at the early stage and at the middle stage getting closer to normal skin in the wound healing process after inflicting the wound, respectively.
Amino Acid Transport System L ; Amino Acid Transport Systems* ; Amino Acids, Essential ; Amino Acids, Neutral ; Animals ; Rats* ; Skin* ; Wound Healing* ; Wounds and Injuries*

The periodontium is a topographically complex organ consisting of epithelial tissue, soft and mineralized tissues. Structures comprising the periodontium include the gingiva, periodontal ligament (PDL), cementum and the alveolar bone. The molecular mechanism of differentiation in PDL fibroblast cells remain unclear. Amino acid transporters play an important role in supplying nutrition to normal and cancer cells and for cell proliferation. Amino acid transport system L is a major nutrient transport system responsible for the Na+-independent transport of neutral amino acids including several essential amino acids. The system L is divided into two major subgroups, the L-type amino acid transporter 1 (LAT1) and the L-type amino acid transporter 2 (LAT2). In this study, the expression pattern of amino acid transport system L was, therefore, investigated in the differentiation of PDL fibroblast cells. To determine the expression level of amino acid transport system L participating in intracellular transport of amino acids in the differentiation of PDL fibroblast cells, it was examined by RT-PCR, observation of cell morphology, Alizaline red-S staining and uptake analysis after inducing experimental differentiation in PDL fibroblast cells isolated from mouse molar teeth. The results are as follows. 1. The LAT1 mRNA was expressed in the early stage of PDL fibroblast cell differentiation. This expression level was gradually reduced by differentiation-inducing time and it was not observed after the late stage. 2. The expression level of LAT2 mRNA was increased in time-dependent manner during differentiation induction of PDL fibroblast cells. 3. There was no changes in the expression level of 4F2hc mRNA, the cofactor of LAT1 and LAT2, during differentiation of PDL fibroblast cells. 4. The expression level of ALP mRNA was gradually increased and the expression level of Col I mRNA was decreased during differentiation of PDL fibroblast cells. 5. The L-leucine transport was reduced by time from the early stage to the late stage in PDL fibroblast cell differentiation. As the results, it is considered that among neutral amino acid transport system L in differentiation of PDL fibroblast cells, the LAT1 has a key role in cell proliferation in the early stage of cell differentiation and the LAT2 has an important role in the late stage of cell differentiation for providing cells with neutral amino acids including several essential amino acids.
Amino Acid Transport System L* ; Amino Acid Transport Systems ; Amino Acids ; Amino Acids, Essential ; Amino Acids, Neutral ; Animals ; Cell Differentiation ; Cell Proliferation ; Dental Cementum ; Fibroblasts* ; Gingiva ; Leucine ; Mice ; Molar ; Periodontal Ligament* ; Periodontium ; RNA, Messenger ; Tooth