Characterization of p-aminohippurate transport from rat kidney which is expressed after injection of size-selected mRNA into oocytes of Xenopus laevis.
First, the existence of an endogenous p-aminohippurate (PAH) transporter in oocytes of Xenopus laevis was demonstrated. When, however, the oocytes were injected with mRNA from rat kidney cortex, an expressed p-aminohippuric acid (PAH) uptake was seen which differed from the endogenous transporter. Both transport systems are saturated at high PAH concentrations, exhibit trans-stimulation by PAH and are partially inhibited by probenecid. The endogenous transport has a rather low affinity for PAH (Km = 0.57 mM) and is about 50% inhibited by probenecid (one apparent inhibition site with half maximal inhibition at 0.5 mM). The expressed PAH transport has a high affinity for PAH (Km = 60 microM) and can be inhibited 80% by probenecid (two apparent inhibition sites with half maximal inhibitions at 1 microM and 2 mM). Expression experiments with fractionated mRNA revealed that the PAH transport expressed from rat kidney cortex is encoded by an mRNA of 1.8 to 2.5 kb.
Steffgen
J
J
Zentrum für Innere Medizin, Universität Ulm, Germany.
Scheyerl
F
F
Gründemann
D
D
Kienle
S
S
Franz
H E
HE
Koepsell
H
H
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D007672:Kidney Cortex / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010316:Particle Size; D011339:Probenecid / Q000494:pharmacology; D012333:RNA, Messenger / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D012964:Sodium / Q000378:metabolism; D014162:Transfection; D014982:Xenopus laevis; D010130:p-Aminohippuric Acid / Q000378:metabolism*
D002352:Carrier Proteins; D012333:RNA, Messenger; D012964:Sodium; D011339:Probenecid; D010130:p-Aminohippuric Acid