Abstract:
:The retinal Na+:Ca2+, K+exchanger cDNA was transiently expressed in human embryonic kidney (HEK 293) cells by transfection with plasmid DNA. The correct targeting of the expressed protein to the plasma membrane was confirmed by immunocytochemistry. The reverse exchange offrent (Ca2+ imported per Na+ extruded) was measured in whole-cell voltage-clamp experiments after intracellular perfusion with Na+ (Na+i, 128 mM) and extracellular perfusion with Ca2+ (Ca2o+, 1 mM) and Ko+ (20 mM). As expected, the exchange current was suppressed by removing Ca2o+. Surprisingly, however, it was also abolished by increasing Na+o to almost abolish the Na+ gradient, and it was almost unaffected by the removal of Ko+. Apparently, then, at variance with the exchanger in the rod outer segment, the retinal exchanger expressed in 293 cells acts essentially as a Na+:Ca2+ exchanger and does not require K+ for its electrogenic activity.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Navanglone A,Rispoli G,Gabellini N,Carafoli Edoi
10.1016/S0006-3495(97)78046-9subject
Has Abstractpub_date
1997-07-01 00:00:00pages
45-51issue
1eissn
0006-3495issn
1542-0086pii
S0006-3495(97)78046-9journal_volume
73pub_type
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