Mechanism of polyamine spermidine uptake by Xenopus laevis oocytes.
In this study, the mechanisms of polyamine spermidine (Spd) uptake were investigated in Xenopus laevis oocytes. Spd uptake followed a sigmoidal kinetics with [S]90/[S]10 = 3 microM and Hill interaction coefficient (n) = 2. The order of magnitude of uptake and efflux was similar (t1/2 = 45 min). The equilibrium potential for Spd, calculated by Nenrst equation, was 90.78 mV. Free energy change for the uptake (delta G) was found to be 2.31 Kcal/mole of Spd. During efflux, Spd was not converted into putrescine or spermine. It seems that there are two types of Spd uptake pathways: Na(+)-dependent and Na(+)-independent since replacement of Na+ from incubation medium did not completely abolish the Spd uptake. The Na(+)-dependent component of Spd uptake was shared neither by system A nor by system ASC amino acids.
Khan
N A
NA
Unité Fonctionnelle de Biologie Cellulaire, CNRS SDI, Faculté de Médecine, C.H.U. de Rennes, France.
Quemener
V
V
Havouis
R
R
Moulinoux
J P
JP
D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D004563:Electrochemistry; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013095:Spermidine / Q000378:metabolism*; D014982:Xenopus laevis
D000596:Amino Acids; D012964:Sodium; D013095:Spermidine