Myocardial Infarction: Cardioprotection by Erythropoietin - Tissue-Protective Cytokines: Methods and Protocols - page 262

therapeutic window, which is also dose-dependent. If treatment is
applied immediately after occlusion, the effective dose can be as
low as 150 IU/kg (9, in rats). 1,000 IU/kg was not effective if
treatment was delayed by 6 h (16, dogs). A single dose applied
immediately after coronary occlusion is as effective as repeated
doses ( 14 ). Moreover, there are some indications that repeated
doses may reduce the effectiveness of treatment ( 10 ). In the only
study in which EPO treatment did not improve the outcome, the
high dose of EPO was applied seven times resulting in the massive
elevation of hematocrit.

A summary of published animal experiments in the in vivo model
of temporary occlusion of a coronary artery followed by reperfu-
sion are summarized in Table 2 .
Based on experimental evidence that EPO attenuates both pri-
mary (apoptotic) and secondary (inflammatory) causes of cell
death, Calvillo et al. ( 18 ) administered 5,000 U/kg i.p. of recom-
binant human EPO (rhEPO) to rats that underwent 30 min isch-
emia followed by reperfusion. rhEPO was given 24 and 0.5 h
before coronary ligation, then daily for 7 days after coronary liga-
tion rhEPO reduced cardiomyocyte loss by approximately 50%,
and accordingly normalized hemodynamic function within 1 week
after reperfusion. RhEPO markedly prevented the apoptosis of cul-
tured adult rat cardiac myocytes subjected to 28 h of hypoxia
(approximately 3% normal oxygen). This in vitro observation sup-
ported the hypothesis that cardiac protective effects of EPO were
independent of hematopoiesis.
Parsa et al. ( 19 ) evaluated the in vivo protective potential of
erythropoietin in the reperfused rabbit heart following 30 min
ventricular ischemia followed by 45 min of reperfusion. They
showed that 5,000 U/kg i.v. EPO given 12 h before ischemia or at
time of coronary ligation limited infarct size and improved global
LV function. However, when EPO was administered at the low
dose of 1,000 U/kg at any time and/or at the time of reperfusion,
it did not improve cardiac function even if significantly reduced
infarct size and incidence of apoptosis in cardiac myocytes. EPO
activated cell survival pathways in myocardial tissue in vivo and in
adult rabbit cardiac fibroblasts in vitro. These pathways, activated
by EPO in both whole hearts and cardiac fibroblasts, are also acti-
vated acutely by ischemia-reperfusion injury.
As part of a study on the effects of EPO on the tissue/organ
injury caused by hemorrhagic shock, endotoxic shock, Abdelrahman
et al. ( 20 ) showed that 300 U/kg i.v. of EPO after 20 min myocar-
dial ischemia right before reperfusion significantly reduced infarct
size in anesthetized rats at 2 h. The administration of the same
dose of EPO before resuscitation abolished the renal dysfunction
and liver injury in hemorrhagic, but not endotoxic, shock at
4-6 h.

1.1.2 Ischemia-
Reperfusion Model