Reduced calcium tolerance in rat cardiomyocytes after myocardial infarction.
During ischaemia and reperfusion the intracellular Na+ concentration is elevated in the cardiomyocytes and the cells are depolarized, both favouring reverse mode Na,Ca-exchange loading of the cell with Ca2+. We examined whether cardiomyocytes from rats with congestive heart failure (CHF) and younger rats (HINCX) which both have a high expression of the Na,Ca-exchanger protein (NCX) showed reduced tolerance to extracellular Ca2+. The CHF was induced in Isofluran anaesthetized rats by left coronary artery ligation. Isolated cardiomyocytes were loaded with Fura-2AM and 140 mm Na+ and exposed to 0.05 mm Ca2+. Expression of the Na,Ca-exchanger protein was analysed. Fura-2 340/380 ratio rose more rapidly in HINCX and CHF than in SHAM, and the rise was abolished by Ni2+. Hypercontracture developed more frequently in HINCX and CHF than in SHAM cells. The amount of NCX was 54% higher in HINCX and 76% higher in CHF compared with SHAM. Na+-loaded cardiomyocytes from CHF and HINCX rats are more susceptible to Ca2+ overload than SHAM cells because of the increased capacity for Na,Ca-exchange.
Sjaastad
I
I
Institute for Experimental Medical Research, University of Oslo, Ullevaal Universityhospital, Oslo, Norway.
Bentzen
J G
JG
Semb
S O
SO
Ilebekk
A
A
Sejersted
O M
OM
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005453:Fluorescence; D006333:Heart Failure / Q000378:metabolism; D008297:Male; D009203:Myocardial Infarction / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism
D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium