Whether the response of the fetal heart to
ischemia-reperfusion is associated with activation of the
c-Jun N-terminal kinase (JNK) pathway is not known. In contrast, involvement of the sarcolemmal L-type Ca2+ channel (LCC) and the mitochondrial KATP (
mitoKATP) channel has been established. This work aimed at investigating the profile of JNK activity during
anoxia-reoxygenation and its modulation by LCC and
mitoK(ATP) channel. Hearts isolated from 4-day-old chick embryos were submitted to
anoxia (30 min) and reoxygenation (60 min). Using the
kinase assay method, the profile of JNK activity in the ventricle was determined every 10 min throughout
anoxia-reoxygenation. Effects on JNK activity of the LCC blocker
verapamil (10 nM), the
mitoK(ATP) channel opener
diazoxide (50 microM) and the blocker
5-hydroxydecanoate (5-HD, 500 microM), the mitochondrial Ca2+ uniporter (MCU) inhibitor
Ru360 (10 microM), and the
antioxidant N-(2-mercaptopropionyl)
glycine (MPG, 1 mM) were determined. In untreated hearts, JNK activity was increased by 40% during
anoxia and peaked fivefold relative to basal level after 30-40 min reoxygenation. This peak value was reduced by half by
diazoxide and was tripled by 5-HD. Furthermore, the 5-HD-mediated stimulation of JNK activity during reoxygenation was abolished by
diazoxide,
verapamil or
Ru360. MPG had no effect on JNK activity, whatever the conditions. None of the tested pharmacological agents altered JNK activity under basal normoxic conditions. Thus, in the embryonic heart, JNK activity exhibits a characteristic pattern during
anoxia and reoxygenation and the respective open-state of LCC, MCU and
mitoKATP channel can be a major determinant of JNK activity in a ROS-independent manner.