Involvement of rBAT in Na(+)-dependent and -independent transport of the neurotransmitter candidate L-DOPA in Xenopus laevis oocytes injected with rabbit small intestinal epithelium poly A(+) RNA.
Although L-3,4-dihydroxyphenylalanine (L-DOPA) is claimed to be a neurotransmitter in the central nervous system (CNS), receptor or transporter molecules for L-DOPA have not been determined. In an attempt to identify a transporter for L-DOPA, we examined whether or not an active and high affinity L-DOPA transport system is expressed in Xenopus laevis oocytes injected with poly A(+) RNA prepared from several tissues. Among the poly A(+) RNAs tested, rabbit intestinal epithelium poly A(+) RNA gave the highest transport activity for L-[(14)C]DOPA in the oocytes. The uptake was approximately five times higher than that of water-injected oocytes, and was partially Na(+)-dependent. L-Tyrosine, L-phenylalanine, L-leucine and L-lysine inhibited this transport activity, whereas D-DOPA, dopamine, glutamate and L-DOPA cyclohexylester, an L-DOPA antagonist did not affect this transport. Coinjection of an antisense cRNA, as well as oligonucleotide complementary to rabbit rBAT (NBAT) cDNA almost completely inhibited the uptake of L-[(14)C]DOPA in the oocytes. On the other hand, an antisense cRNA of rabbit 4F2hc barely affected this L-[(14)C]DOPA uptake activity. rBAT was thus responsible for the L-[(14)C]DOPA uptake activity expressed in X. laevis oocytes injected with poly A(+) RNA from rabbit intestinal epithelium. As rBAT is localized at the target regions of L-DOPA in the CNS, rBAT might be one of the components involved in L-DOPAergic neurotransmission.
Ishiia
H
H
Department of Pharmacology, Yokohama City University of Medicine, Yokohama, Japan.
Sasaki
Y
Y
Goshima
Y
Y
Kanai
Y
Y
Endou
H
H
Ayusawa
D
D
Ono
H
H
Miyamae
T
T
Misu
Y
Y
D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D007413:Intestinal Mucosa / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism; D007477:Ions; D007700:Kinetics; D007980:Levodopa / Q000493:pharmacokinetics*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008845:Microinjections / Q000379:methods; D018377:Neurotransmitter Agents / Q000493:pharmacokinetics*; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000008:administration & dosage / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D014982:Xenopus laevis
D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D002352:Carrier Proteins; D007477:Ions; D008562:Membrane Glycoproteins; D018377:Neurotransmitter Agents; D012333:RNA, Messenger; C082087:rBAT protein, Oryctolagus cuniculus; D007980:Levodopa; D012964:Sodium