Influx of L-arginine is an indicator of membrane potential in human fibroblasts.
The net influx of L-arginine (JARG) was employed as an indicator of the membrane potential in human fibroblasts. Cell depolarization, obtained by increasing [K+]out, decreased both JARG and the net influx of the lipid soluble cation tetraphenylphosphonium (JTPP), a probe of membrane potential. JTPP, but not JARG, was influenced by the mitochondrial potential and exhibited a component dependent on intracellular and/or extracellular binding. JARG was sensitive to changes in the membrane potential induced by Na+-dependent transport of L-proline or by the activity of Na+-K+-ATPase. In the presence of 50 microM valinomycin, JARG was markedly influenced by the distribution ratio of K+ in a range of [K+]out from 1.5 to 100 mM. In this range of [K+]out, membrane potential (Em) varied from -90 to -23 mV, and calibration of JARG vs. the membrane potential yielded a linear relationship. These results indicate the following: 1) that the net influx of TPP+ is not a reliable indicator of membrane potential in cultured human fibroblasts; 2) that in the same cells the net influx of L-arginine can be employed as an index of membrane potential; 3) that in a range of Em from -23 to -90 mV the activity of system y+ (the membrane agency devoted to L-arginine transport in cultured human fibroblasts) exhibits no saturation of potential-dependent activation of transport.
Bussolati
O
O
Istituto di Patologia Generale, Universitá, di Parma, Italy.
Laris
P C
PC
Nucci
F A
FA
Dall'Asta
V
V
Franchi-Gazzola
R
R
Guidotti
G G
GG
Gazzola
G C
GC
D001120:Arginine / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D005347:Fibroblasts / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000502:physiology; D009861:Onium Compounds / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014634:Valinomycin / Q000494:pharmacology
D009861:Onium Compounds; D009943:Organophosphorus Compounds; D014634:Valinomycin; D001120:Arginine; D011392:Proline; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; C013289:tetraphenylphosphonium