Neuronal expression of sodium/bicarbonate cotransporter NBCn1 (SLC4A7) and its response to chronic metabolic acidosis.
The sodium-bicarbonate cotransporter NBCn1 (SLC4A7) is an acid-base transporter that normally moves Na(+) and HCO(3)(-) into the cell. This membrane protein is sensitive to cellular and systemic pH changes. We examined NBCn1 expression and localization in the brain and its response to chronic metabolic acidosis. Two new NBCn1 antibodies were generated by immunizing a rabbit and a guinea pig. The antibodies stained neurons in a variety of rat brain regions, including hippocampal pyramidal neurons, dentate gyrus granular neurons, posterior cortical neurons, and cerebellar Purkinje neurons. Choroid plexus epithelia were also stained. Double immunofluorescence labeling showed that NBCn1 and the postsynaptic density protein PSD-95 were found in the same hippocampal CA3 neurons and partially colocalized in dendrites. PSD-95 was pulled down from rat brain lysates with the GST/NBCn1 fusion protein and was also coimmunoprecipitated with NBCn1. Chronic metabolic acidosis was induced by feeding rats with normal chow or 0.4 M HCl-containing chow for 7 days. Real-time PCR and immunoblot showed upregulation of NBCn1 mRNA and protein in the hippocampus of acidotic rats. NBCn1 immunostaining was enhanced in CA3 neurons, posterior cortical neurons, and cerebellar granular cells. Intraperitoneal administration of N-methyl-d-aspartate caused neuronal death determined by caspase-3 activity, and this effect was more severe in acidotic rats. Administering N-methyl-d-aspartate also inhibited NBCn1 upregulation in acidotic rats. We conclude that NBCn1 in neurons is upregulated by chronic acid loads, and this upregulation is associated with glutamate excitotoxicity.
Park
Hae Jeong
HJ
Dept. of Physiology, Emory Univ., Atlanta, GA 30322, USA.
Rajbhandari
Ira
I
Yang
Han Soo
HS
Lee
Soojung
S
Cucoranu
Delia
D
Cooper
Deborah S
DS
Klein
Janet D
JD
Sands
Jeff M
JM
Choi
Inyeong
I
D000138:Acidosis / Q000097:blood / Q000139:chemically induced / Q000378:metabolism* / Q000652:urine; D000818:Animals; D000906:Antibodies; D001639:Bicarbonates / Q000097:blood; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death; D005786:Gene Expression Regulation; D006168:Guinea Pigs; D006624:Hippocampus / Q000166:cytology; D006863:Hydrogen-Ion Concentration; D009474:Neurons / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D027982:Sodium-Bicarbonate Symporters / Q000235:genetics / Q000378:metabolism*; D014556:Urine / Q000737:chemistry
D000906:Antibodies; D001639:Bicarbonates; D012333:RNA, Messenger; C498902:Slc4a7 protein, rat; D027982:Sodium-Bicarbonate Symporters; D053148:Caspase 3