Possible expression of functional glutamate transporters in the rat testis.
Neither expression nor functionality is clear in peripheral tissues with the molecular machineries required for excitatory neurotransmitter signaling by L-glutamate (Glu) in the central nervous system, while a recent study has shown that several Glu receptors are functionally expressed in the rat testis. This fact prompted us to explore the possible functional expression in the rat testis of the Glu transporters usually responsible for the regulation of extracellular Glu concentrations in the brain. RT-PCR revealed the expression, in the rat testis, of mRNA for five different subtypes of Glu transporters, in addition to that for particular subtypes of ionotropic and metabotropic Glu receptors. Glutamate transporter-1 (GLT-1) was different in the brain from that in the testis in terms of molecular sizes on Northern and Western blot analyses. In situ hybridization as well as immunohistochemical analysis showed localized expression of glutamate aspartate transporter at interstitial spaces and GLT-1 at elongated spermatids in the rat testis respectively. The expression of mRNA was localized for excitatory amino acid transporter-5 at the basal compartment of the seminiferous tubule in the rat testis. [(3)H]Glu was accumulated in testicular crude mitochondrial fractions in a temperature- and sodium-dependent saturable manner with pharmacological profiles similar to those shown in brain crude mitochondrial fractions. These results suggested that particular subtypes of central Glu transporters for the regulation of extracellular Glu concentrations in the rat testis could be constitutively and functionally expressed.
Takarada
T
T
Laboratory of Molecular Pharmacology, Kanazawa University Graduate School of Natural Science and Technology, 13-1 Takara-machi, Kanazawa, Ishikawa 920-0934, Japan.
Hinoi
E
E
Balcar
V J
VJ
Taniura
H
H
Yoneda
Y
Y
D027322:Amino Acid Transport System X-AG / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D026905:Amino Acid Transport Systems; D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D002352:Carrier Proteins / Q000235:genetics; D027342:Excitatory Amino Acid Transporter 2 / Q000235:genetics; D050582:Excitatory Amino Acid Transporter 5; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D010786:Photoreceptor Cells; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000235:genetics; D013737:Testis / Q000737:chemistry* / Q000378:metabolism
D027322:Amino Acid Transport System X-AG; D026905:Amino Acid Transport Systems; D002352:Carrier Proteins; D027342:Excitatory Amino Acid Transporter 2; D050582:Excitatory Amino Acid Transporter 5; D050491:Glutamate Plasma Membrane Transport Proteins; D012333:RNA, Messenger; D017470:Receptors, Glutamate; C484554:Slc1a7 protein, rat; D027981:Symporters; D018698:Glutamic Acid