Journal Article

Increased effects of C‐type natriuretic peptide on contractility and calcium regulation in murine hearts overexpressing cyclic GMP‐dependent protein kinase I

Wollert, Kai C, Yurukova, Sevdalina, Begrow, Frank, Kilic, Ana, Kuhn, Michaela, Gambaryan, Stepan, Lohmann, Suzanne M, Fiedler, Beate, Walter, Ulrich

2003

Overview

C‐type natriuretic peptide (CNP) and its receptor guanylyl cyclase (GC‐B) are expressed in the heart and modulate cardiac contractility in a cGMP‐dependent manner. Since the distal cellular signalling pathways remain unclear, we evaluated the peptide effects on cardiac function and calcium regulation in wild‐type (WT) and transgenic mice with cardiac overexpression of cGMP‐dependent protein kinase I (PKG ITG). In isolated, perfused working WT hearts, CNP (10 nM) provoked an immediate increase in the maximal rates of contraction and relaxation, a small increase in the left ventricular systolic pressure and a decrease in the time of relaxation. These changes in cardiac function were accompanied by a marked increase in the levels of Ser16‐phosphorylated phospholamban (PLB). In PKG ITG hearts, the effects of CNP on cardiac contractility and relaxation as well as on PLB phosphorylation were markedly enhanced. CNP increased cell shortening and systolic Cai2+ levels, and accelerated Cai2+ decay in isolated, Indo‐1/AM‐loaded WT cardiomyocytes, and these effects were enhanced in PKG I‐overexpressing cardiomyocytes. 8‐pCPT‐cGMP, a membrane‐permeable PKG activator, mimicked the contractile and molecular actions of CNP, the effects again being more pronounced in PKG ITG hearts. In contrast, the cardiac reponses to β‐adrenergic stimulation were not different between genotypes. Taken together, our data indicate that PKG I is a downstream target activated by the CNP/GC‐B/cGMP‐signalling pathway in cardiac myocytes. cGMP/PKG I‐stimulated phosphorylation of PLB and subsequent activation of the sarcoplasmic reticulum Ca2+ pump appear to mediate the positive inotropic and lusitropic responses to CNP. British Journal of Pharmacology (2003) 140, 1227–1236. doi:10.1038/sj.bjp.0705567

• Publisher: Blackwell Publishing Ltd,Nature Publishing
• Subject: Animals / Biological and medical sciences / Blotting, Western / Calcium - physiology / calcium regulation / cardiac contractile function / cGMP‐dependent protein kinase type I / Cyclic GMP-Dependent Protein Kinase Type I / Cyclic GMP-Dependent Protein Kinases - metabolism / C‐type natriuretic peptide / Heart Ventricles - cytology / Humans / Kinetics / Medical sciences / Mice / Mice, Transgenic / Myocardial Contraction - drug effects / Myocardial Contraction - physiology / Myocytes, Cardiac - drug effects / Myocytes, Cardiac - physiology / Natriuretic Agents - pharmacology / Natriuretic Peptide, C-Type - pharmacology / Pharmacology. Drug treatments / transgenic mice