The effect of ERK and p38 MAPK kinase inhibition on ET-1–induced ATF3 expression.

<p>ERK inhibitor PD98059 (10 µM) (<b>A, C</b>) or p38 inhibitor SB203580 (10 µM) (<b>B, D</b>) were added to culture medium of neonatal rat cardiomyocyte cell cultures and 2 hours later ET-1 (100 nM) was added to medium for 1 hour. DMSO was used as a control. <b>A, B,</b> ATF3 mRNA levels were determined by qPCR and normalized to 18S quantified from the same samples. The mRNA levels are presented relative to non-stimulated DMSO control cells. The results represent mean ± SEM (n = 3–19) from at least 3 independent experiments. <b>C, D,</b> ATF3 and GAPDH protein levels were detected by Western blotting and representative Western blots are shown. ATF3 protein levels were normalized with GAPDH levels and are presented relative to non-stimulated DMSO control cells. Bar graphs represent mean ± SEM (n = 6–10) from at least 3 independent experiments. ** <i>P<</i>0.01; ***<i>P<</i>0.001.