Simulated ischaemia causes both necrotic and apoptotic death of primary cul
tures of neonatal rat cardiac myocytes. Simulated ischaemia is associated w
ith increased expression of urocortin mRNA and with the release of urocorti
n peptide into the medium. Exogenous urocortin is more potent than corticot
ropin releasing hormone (CRH) in protecting cardiac myocytes from necrotic
and apoptotic death induced by ischaemia, and the cardioprotective effects
of ischaemia-preconditioned media are abrogated by antagonists: to the CRH
family of peptides. Simulated ischaemia increases cardiac myocyte expressio
n of CCAAT enhancer binding (C/EBP) transcription factors, and of the p65 s
ubunit of NF kappa B, and reporter activity of a construct incorporating a
fragment of the urocortin promoter containing a C/EBP consensus site is als
o enhanced by simulated ischaemia. The data suggest that ischaemia, acting
partly through increased expression of C/EBP transactivators, increases exp
ression of urocortin mRNA, which is rapidly translated to the mature form.
The mature peptide:is rapidly released, and exerts autocrine/paracrine prot
ective effects through the cardiac CRH-R2 receptor which preferentially bin
ds urocortin. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.