title: Activation of protein kinase A by atrial natriuretic peptide in neonatal rat cardiac fibroblasts: role in regulation of the local renin-angiotensin system.
abstract: There is an inverse relationship between renin and atrial natriuretic peptide (ANP) levels in the plasma. Since both the ANP and renin-angiotensin system (RAS) are upregulated in development and cardiac hypertrophy, we tested whether ANP differentially regulates RAS in cardiac cells. Cardiac fibroblasts isolated from neonatal rats were treated with ANP(1-28), a biologically active fragment of ANP. Renin and angiotensinogen (Ao) mRNA levels were measured by quantitative multiplex RT-PCR and protein levels determined by Western blot analysis. ANP(1-28) increased renin and Ao mRNA levels (737+/-131% and 178+/-51.3%) with EC50 values of 4.12+/-0.3 and 8.67+/-0.22 nmol/L, respectively. At the protein level, secretion of renin and Ao was significantly enhanced resulting in approximately 4-fold increase in ANG II level in the medium. The effect of ANP(1-28) on renin and Ao mRNA expression were reproduced by 8-bromo-cyclic GMP. Inhibition of protein kinase G (PKG) with KT5823 blunted ANP(1-28)-induced upregulation of renin, but not Ao mRNA, while inhibition of protein kinase A (PKA) with KT5720 attenuated the upregulation of both renin and Ao mRNA. These findings suggest that unlike in plasma, ANP positively regulates the RAS in cardiac fibroblasts, which may have a significant role in development of the fetal heart.
authors.affiliation: Division of Molecular Cardiology, Cardiovascular Research Institute, The Texas A&M University System Health Science Center, College of Medicine, TX, USA.
authors.forename: Sandhya
authors.initials: S
authors.lastname: Sanghi
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Manuela
authors.initials: M
authors.lastname: Smith
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Baker
authors.forename: David E
authors.initials: DE
authors.lastname: Dostal
mesh_terms: D000804:Angiotensin II / Q000096:biosynthesis; D000808:Angiotensinogen / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000502:physiology*; D002227:Carbazoles / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation; D007211:Indoles / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D012083:Renin / Q000096:biosynthesis* / Q000235:genetics; D012084:Renin-Angiotensin System / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D002227:Carbazoles; D007211:Indoles; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D000808:Angiotensinogen; D000804:Angiotensin II; C073601:KT 5823; C016276:8-bromocyclic GMP; D009320:Atrial Natriuretic Factor; D017868:Cyclic AMP-Dependent Protein Kinases; D012083:Renin; D006152:Cyclic GMP