Low-flow ischemia and hypoxia stimulate apoptosis in perfused hearts independently of reperfusion.
Post-ischemic reperfusion leads to apoptosis-linked loss of myocytes in cultured cells and in vivo. We tested the hypothesis that apoptosis develops without reperfusion in Langendorff-perfused hearts exposed to either low-flow ischemia (LFI) or hypoxia (H). Rat hearts were perfused with amino-acid-enriched Krebs-Henseleit buffer and exposed for 6 h to LFI (flow=2 ml/min, PO(2)=500+/-50mmHg, mean+/-SD), H (10ml/min, 120+/-15mmHg), or control conditions (C, 10ml/min, 500+/-50mmHg). At selected times, DNA-fragmentation was measured by agarose-gel electrophoresis and in situ TUNEL assay. After 6 h, the ratio (TUNEL-positive)/(total nuclei) was 0.620+/-0.027, 0.615+/-0.005, 0.404+/-0.021 in LFI, H and C, respectively. The ratio was 0.813+/-0.021 in hearts exposed to 90 min global no-flow ischemia and reperfused (5 h). To assess the role of membrane-diffusible factors, separate experiments were performed recirculating the medium and exposing hearts to LFI or H as above. The degree of apoptosis was the same in both the recirculating and non-recirculating modes. Thus, apoptosis develops by similar extents and in a time-dependent fashion in crystalloid-perfused rat hearts during LFI or H at the same oxygen shortage (flow.PO(2)), even without the reperfusion.
Pozzi
Silvia
S
Department of Medicine, Surgery and Dentistry, University of Milan, San Paolo Hospital, via di Rudini 8, I-20142 Milan, Italy.
Malferrari
Giulia
G
Biunno
Ida
I
Samaja
Michele
M
D000818:Animals; D017209:Apoptosis; D004247:DNA / Q000032:analysis / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D006339:Heart Rate; D000860:Hypoxia / Q000473:pathology* / Q000503:physiopathology; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D008297:Male; D017202:Myocardial Ischemia / Q000473:pathology* / Q000503:physiopathology; D015425:Myocardial Reperfusion / Q000379:methods*; D009206:Myocardium / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000473:pathology / Q000503:physiopathology; D013995:Time
D004247:DNA