Endothelin-3 induces hypertrophy of cardiomyocytes by the endogenous endothelin-1-mediated mechanism

Abstract

We have recently reported that endothelin-1 (ET-1) mediates angiotensin II-induced hypertrophy of cardiomyocytes as an autocrine/paracrine factor. In the present study, we examined whether endothelin-3 (ET-3) induces hypertrophy of cultured neonatal rat cardiomyocytes and whether endogenous ET-1 mediates this effect. ET-3 (10-7 M) increased the cell surface area of cardiomyocytes after 48 h. ET-3 dose dependently (10-9-10-7 M) stimulated protein synthesis as evaluated by [3H]leucine incorporation; the maximum response was 1.4-fold increase over the control at 10-7 M. Since the response of cardiac hypertrophy is characterized by enhanced expression of fetal isoforms of muscle specific genes, the effect of ET-3 on steady state levels of mRNA for skeletal α-actin was evaluated by Northern blot analysis. ET- 3 (10-9-10-7 M) increased mRNA level for skeletal α-actin with a maximum response after 6 h. ET-3-induced [3H]leucine incorporation, skeletal α-actin mRNA and cell surface area were inhibited by a synthetic ET(B) receptor antagonist (BQ788). Interestingly, ET-3-induced skeletal α-actin gene expression and [3H]leucine incorporation were inhibited by a synthetic ET(A) receptor antagonist (BQ123) as well as by antisense oligonucleotides against peproET-1 mRNA. ET-3 (10-7 M) transiently increased mRNA levels for ET-1 peaking at 30 min and stimulated the release of immunoreactive ET-1 from cardiomyocytes. These results suggest that endogenous ET-1 locally generated and secreted by cardiomyocytes may contribute to ET-3-induced cardiac hypertrophy as an autocrine/paracrine factor.