The action of oxidized low density lipoprotein on calcium transients in isolated rabbit cardiomyocytes.
The effect of oxidized low density lipoprotein (oxLDL) on the Ca2+ transients of isolated rabbit cardiomyocytes was assessed. LDL was oxidized by a free radical generating system in vitro. The systolic Ca2+ concentration in transients was significantly increased after treatment with 100 micrograms of oxLDL cholesterol/ml for 16 min without having any effect on the diastolic [Ca2+]. However, a toxic effect was observed when the concentration of oxLDL was increased to 1,000 micrograms/ml. Cells treated with 100 micrograms of oxLDL/ml were more sensitive to the blocking action of nicardipine on the Ca2+ transient than were control cardiomyocytes. Furthermore, oxLDL failed to produce a stimulatory effect on the transient when the extracellular [Ca2+] was lowered. The malondialdehyde content in the oxLDL correlated well with the change in systolic [Ca2+] of treated cells. Lazaroid, a novel antioxidant, completely inhibited malondialdehyde formation in the oxLDL and prevented the increment of systolic [Ca2+] in the treated cells. The data indicate that oxLDL can induce relatively rapid alterations in cellular Ca2+ transients via a modification of Ca2+ entry through the L-type Ca2+ channel. LDL oxidation induced by free radicals may play an important role in influencing cardiac contractile function during pathological conditions such as ischemia/reperfusion challenge.
Liu
K
K
Ion Transport Laboratory, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
Massaeli
H
H
Pierce
G N
GN
D000818:Animals; D000975:Antioxidants; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006321:Heart / Q000187:drug effects*; D008054:Lipid Peroxides / Q000037:antagonists & inhibitors; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009529:Nicardipine / Q000494:pharmacology; D010084:Oxidation-Reduction; D011281:Pregnatrienes / Q000494:pharmacology; D011817:Rabbits
D000975:Antioxidants; D008054:Lipid Peroxides; D008077:Lipoproteins, LDL; D011281:Pregnatrienes; D008315:Malondialdehyde; D009529:Nicardipine; C053356:U 74500A; D002118:Calcium