Cardiomyocytes were exposed to PE or ET-1 for the times indicated. RNA expression profiling was performed using Affymetrix rat 230 2.0 microarrays (A and C) or Affymetrix rat exon 1.0 ST arrays (B). (A) Heatmaps for transcriptional changes at 24 h clustered according to similarity of response to PE compared with ET-1 (range: cyan=−2.5; black=0; red=2.5; log₂ scale). Results are means for n=3 independent hybridizations of different samples each prepared from three cardiomyocyte preparations. (B) k-Means clustering of mRNAs regulated by PE at 0.5 or 1 h. (C) k-Means clustering of RNAs regulated by PE at 2, 4 or 24 h. (B and C) Results (means for n=3 hybridizations) are shown for each RNA. Numbers of transcripts in each cluster are in parentheses.