Relative expression of ETA-R, ETB-R, ppET-1 and ECE in the left ventricular tissue obtained from the three groups (S=sham, Ov=ovariectomized, E2=E2 substituted-ovariectomized). Expression levels for each target gene have been normalized to the mean expression of sham-operated rats taken as a value of 1. Expression level of ETB-R mRNA was significantly upregulated in estrogen-deficient rats, whereas there was no significant difference between the three groups concerning expression levels of ETA-R, ECE and ppET-1 (*P<0.005 vs S and vs E2, n=10 for each treatment group).