Regional difference of glutamate-induced swelling in cultured rat brain astrocytes.
L-glutamate (glutamate) is an important neurotoxin as well as the major excitatory neurotransmitter. Extracellular glutamate levels are elevated following ischemia, hypoglycemia, and trauma. One consequence of elevated glutamate levels is cell swelling. Such swelling occurs primarily in astroglial cells. We characterized the regional difference in glutamate-induced swelling response of cultured astrocytes from rat cerebral cortex, hippocampus and cerebellum. Glutamate produced dose-dependent astrocytic swelling in both cerebral cortex and hippocampus, showing a maximal effect in 0.5 mM concentration, as measured by 3-O-methyl-D-[1-3H]glucose uptake. However, in cerebellum, glutamate did not produce astrocytic swelling. It has been suggested that Na+ -dependent glutamate uptake is a possible mechanism of glutamate-induced swelling. The Vmax for glutamate uptake into cerebellum astrocytes was significantly lower (6.7 nmol/mg protein/min) than those for cerebral cortex and hippocampus astrocytes (13.0 and 12.0 nmol/mg protein/min, respectively). In three regions, more than 90% of the cultured cells showed glial fibrillary acidic protein (GFAP) immunoreactivity. Immunoreactivity of GLT, one of the markers of glutamate transporters, which is expressed at low levels in cultured astrocytes, did not show any differences in three regions. However, immunoreactivities of GLAST, the other astroglial glutamate transporter, and aquaporin4 (APQ4), a water transporter, were significantly higher in cerebral cortex and hippocampus than in cerebellum. These results may explain the regional difference of glutamate-induced astrocytic swelling.
Han
Byung Cheol
BC
College of Veterinary Medicine and Research Institute of Veterinary Medicine, Chungbuk National University, San 48, Kaeshin-Dong, Heungduk-Ku, Cheongju, Chungbuk, 361-763, Republic of Korea.
Koh
Sang Bum
SB
Lee
Eun Young
EY
Seong
Yeon Hee
YH
D027322:Amino Acid Transport System X-AG / Q000096:biosynthesis; D000818:Animals; D000831:Animals, Newborn; D051401:Aquaporin 4; D020346:Aquaporins / Q000096:biosynthesis; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D027322:Amino Acid Transport System X-AG; C496032:Aqp4 protein, rat; D051401:Aquaporin 4; D020346:Aquaporins; D005904:Glial Fibrillary Acidic Protein; D018698:Glutamic Acid