Na+/H+ exchange and L-DOPA handling in OK cells.

• Type: Other Publications
• Date: 1998

Authors

Pedro Gomes (Author) Other; soares-da-silva, p (Author) FMUP

Other information

Authenticus ID: P-001-893

Abstract (EN): In the present study the influence of Na+ and the Na+/H+ exchanger upon L-DOPA uptake by OK cells applied from the apical and basal cell borders was determined. Cells were cultured in polycarbonate filters and a non-saturating concentration of L-DOPA (25 ¿M) was applied from the apical or basal cell border. Uptake and flux were measured over a 6 min period. Osmolarity was maintained by replacing Na+ by choline. Reducing apical Na+ (from 137 to 0 mM) without changing basal Na+ (137 mM) produced a 37% reduction in apical uptake without changing apical-to-basal flux or basal extrusion of L-DOPA. Amiloride (100 ¿M) applied apically produced no change in apical uptake of L-DOPA, but reduced the apical-to-basal flux and the basal extrusion of L-DOPA by 41 to 49%. A similar effect was observed when pH at the apical cell border was lowered from 7.4 to 6.9. A further reduction in apical pH to 6.4 decreased apical uptake of L-DOPA (21% reduction) and markedly reduced the apical-to-basal flux and the basal extrusion of L-DOPA by 40 to 60%. The rise of apical pH from 7.4 to 7.9 increased apical uptake of L-DOPA without changes in apical-to-basal flux and basal extrusion of L-DOPA. The basal uptake of L-DOPA was Na+-independent and basal-to-apical flux and apical extrusion of L-DOPA were enhanced during stimulation of apical Na+/H+ exchange. Na+ and Na+/H+ exchange appear to have important roles in L-DOPA uptake and extrusion.

Language: English

Type (Professor's evaluation): Scientific