adrenomedullin and Cicatrix

The present study examined whether natriuretic peptide expression in the scar of post-myocardial infarcted (MI) rats was derived at least in part by residing myofibroblasts. ANP and BNP mRNA levels were significantly increased in the non-infarcted left ventricle and scar of 1-week post-MI male rats, as compared to the left ventricle of normal rats. The infarct region contained myofibroblasts and contracted cardiac myocytes residing predominantly in the epicardial border zone. In primary passage scar-derived myofibroblasts, alpha-myosin heavy chain mRNA was undetectable, whereas ANP, BNP, as well as adrenomedullin and corin mRNA expression persisted. In 1-3 day cultured primary passage myofibroblasts, prepro-ANP, mature ANP, and BNP staining was observed in the cytoplasm/perinuclear region co-incident with unorganized alpha-smooth muscle actin. Following 4-7 days in culture, myofibroblasts expressed organized alpha-smooth muscle actin filaments. However, natriuretic peptides were predominantly detected in the nucleus and cytoplasm, and thin filaments occupying the perinuclear region were positive for prepro-ANP and BNP. Isoproterenol treatment of first passage scar myofibroblasts increased protein synthesis and induced BNP mRNA expression, whereas ANP mRNA levels remained unchanged. By contrast, neither ANP nor BNP mRNAs were induced following exposure to AII despite increased protein synthesis. These data highlight the novel observation that scar myofibroblasts synthesized ANP, BNP, adrenomedullin, and expressed the pro-convertase corin. Constitutive and sympathetic-driven natriuretic peptide synthesis by myofibroblasts may in part influence reparative fibrosis.

Topics: Adrenomedullin; Angiotensin II; Animals; Animals, Newborn; Atrial Natriuretic Factor; Cells, Cultured; Cicatrix; Colforsin; Dose-Response Relationship, Drug; Fibroblasts; Gene Expression; Isoproterenol; Male; Myocardial Infarction; Myocytes, Cardiac; Natriuretic Peptide, Brain; Peptides; Protein Biosynthesis; Rats; Rats, Sprague-Dawley; RNA, Messenger; Serine Endopeptidases

Adrenomedullin (AM) is a strong vasodilator peptide with proven antimitogenic and antiproliferative effects in renal mesangial cells, as well as diuretic and natriuretic actions. Its gene expression is stimulated by endotoxins (lipopolysacharides) and cytokines. Consequently, its plasma and urinary levels are known to deviate from normal levels in many renal diseases. The purpose of this study is to determine plasma and urinary AM levels in children with renal parenchymal scar (RPS) and vesicoureteral reflux (VUR). The study was carried out on 74 children with recurrent urinary tract infections, arranged in groups: 25 patients with RPS with VUR (group I), 16 patients with RPS without VUR (group II), 12 patients with VUR without RPS (group III) and 21 healthy children as the control group. Plasma and urinary AM concentrations were both determined by high performance liquid chromotography (HPLC). Plasma AM was measured as picomoles per milliliter (pM/ml) and urinary AM as pM/mg urinary creatinine. In addition, serum creatinine, creatinine clearance and fractional sodium excretion (FE(Na)) were measured. All cases with RPS and VUR had normal blood pressure levels. The plasma AM levels were higher, although not significantly, in the control group (56.2+/-14.0 pM/ml) than in group I (50.6+/-4.2 pM/ml), group II (49.6+/-3.7 pM/ml) and group III (50.6+/-3.6 pM/ml) ( P =0.162). The urinary AM levels were higher in the control group (80.1+/-33.9 pM/mg) than in the three study groups (52+/-7.6 pM/mg, 58.6+/-7.5 pM/mg and 44.2+/-6.4 pM/mg; P =0.003, P =0.002 and P =0.002, respectively). There were no differences among the 4 groups (group I, group II, group III and the control group) in terms of FE(Na) and creatinine clearance ( P >0.05 and P >0.05, respectively). The finding that diminished urinary AM levels in patients with RPS and VUR implies that AM can be a prognostic factor in the long-term follow-up of cases with these diseases.

Topics: Adolescent; Adrenomedullin; Child; Child, Preschool; Cicatrix; Humans; Infant; Kidney; Peptides; Urinary Tract Infections; Vesico-Ureteral Reflux