Endothelin-1 (ET-1) is believed to play an important role in cardiac ischaemia/
reperfusion injury. ET-1 is synthesized from preproET-1 by the action of ET-converting
enzyme (ECE). It is unclear to what extent the ET system is activated following prolonged ischaemia. In this study we used a model mimicking the conditions of the donor heart during
transplantation. Isolated rat hearts perfused with
Krebs-Henseleit buffer were subjected to 30 min of normothermic perfusion, then 4 h of cardioplegic arrest at 4 degrees C with St Thomas' Hospital
solution, followed by reperfusion for 2 h. Hearts were freeze-clamped at different time points during the protocol. Using quantitative reverse transcription-PCR, relative levels of ET-1 and ECE
mRNA expression were measured and compared with a housekeeping gene (
ribosomal protein L32). During reperfusion there was a consistent decrease in coronary flow to approx. 85-90% of pre-ischaemic flow. There was no significant alteration in preproET-1
mRNA expression during 2 h of reperfusion. However, ECE
mRNA expression was increased by 77.5% at 1 h and by 74.6% at 2 h following ischaemia compared with pre-ischaemic values (P<0.05). Thus we conclude that ECE
mRNA expression is increased following prolonged hypothermic cardioplegic arrest. Elevations in the expression of this
enzyme may help to explain the role of the ET system in the pathogenesis of ischaemia/
reperfusion injury following cardiac surgery and
transplantation.