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Research Article

Endothelin-1 is an autocrine/paracrine factor in the mechanism of angiotensin II-induced hypertrophy in cultured rat cardiomyocytes.

H Ito, Y Hirata, S Adachi, M Tanaka, M Tsujino, A Koike, A Nogami, F Murumo and M Hiroe

Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.

Published July 1993

To elucidate the cellular mechanism by which angiotensin II (ANG II) induces cardiac hypertrophy, we investigated the possible autocrine/paracrine role of endogenous endothelin-1 (ET-1) in ANG II-induced hypertrophy of neonatal rat cardiomyocytes by use of synthetic ET-1 receptor antagonist and antisense oligonucleotides to preproET-1 (ppET-1) mRNA. Northern blot analysis and in situ hybridization revealed that ppET-1 mRNA was expressed in cardiomyocytes, but, to a lesser extent, in nonmyocytes as well. ANG II upregulated ppET-1 mRNA level by threefold over control level as early as 30 min, and it stimulated release of immunoreactive ET-1 from cardiomyocytes in a dose- and time-dependent manner. ET-1 stimulated ppET-1 mRNA levels after 30 min in a similar fashion as ANG II. Tetradecanoylphorbol-acetate (10(-7) M) mimicked the effects of ANG II and ET-1 on induction of ppET-1 mRNA. ANG II-induced ppET-1 gene expression was completely blocked by protein kinase C inhibitor H-7 or by down-regulation of endogenous protein kinase C by pretreatment with phorbol ester. ET-1 and ANG II stimulated twofold increase [3H]leucine incorporation into cardiomyocytes, whose effects were similarly and dose dependently inhibited by endothelin A receptor antagonist (BQ123). Introduction of antisense sequence against coding region of ppET-1 mRNA into cardiomyocytes resulted in complete blockade with ppET-1 mRNA levels and [3H]leucine incorporation stimulated by ANG II. These results suggest that endogenous ET-1 locally generated and secreted by cardiomyocytes may contribute to ANG II-induced cardiac hypertrophy via an autocrine/paracrine fashion.

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