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  • Title: Expression and function of LAT1, a neutral amino acid exchanger, in renal porcine epithelial cell line LLC-PK.
    Author: Soares-da-Silva P, Serrão P, Fraga S, Pinho MJ.
    Journal: Acta Physiol Scand; 2005 Sep; 185(1):71-8. PubMed ID: 16128699.
    Abstract:
    AIM: The present study examined the expression of LAT1 and the functional characteristics of the inward and outward [14C] l-leucine transporter in the renal porcine epithelial cell line LLC-PK1. METHODS: LLC-PK1 cells were cultured in polycarbonate filters and accumulation and transepithelial flux of the substrate monitored with [14C] l-leucine. LAT1 transcripts were examined by RT-PCR. LAT1 protein was detected by immunoblotting. RESULTS: The accumulation of [14C] l-leucine in the cell and the [14C] l-leucine transepithelial flux were four- and twofold, respectively, when the substrate was added from the basal cell side, suggesting that the basolateral membrane is endowed with a high density of transport units, when compared with the apical membrane. Increases in the transepithelial flux of [14C] l-leucine by unlabelled l-leucine were also more pronounced when unlabelled l-leucine was added from the basolateral membrane. In the absence of Na+, unlabelled l-leucine increased the basal and apical fractional outflow of [14C] l-leucine, this being similar at pH 7.4 and pH 6.2. RT-PCR and immunoblotting detected LAT1 transcript and protein, respectively. CONCLUSION: LLC-PK1 cells are endowed with the LAT1 transcript and protein and transport l-leucine through the Na+-independent and pH-insensitive LAT1 transporter. The density of transporter units in LLC-PK1 cells may be higher at the basolateral membranes, although be also present in the apical membranes.
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