Pressure- and Volume-Induced Left Ventricular Hypertrophies Are Associated With Distinct Myocyte Phenotypes and Differential Induction of Peptide Growth Factor mRNAs

Abstract

Background Chronic pressure and volume overload (PO and VO) result in morphologically and functionally distinct forms of myocardial hypertrophy. We tested the hypothesis that PO- and VO-induced left ventricular (LV) hypertrophies are associated with distinct molecular phenotypes and patterns of peptide growth factor induction. Methods and Results mRNA levels were quantified in LV myocardium from rats with LV hypertrophy due to PO or VO caused by suprarenal aortic constriction or an abdominal aortocaval fistula, respectively, for 1 week. Although PO and VO caused comparable increases in LV weight and prepro–atrial natriuretic factor mRNA, PO but not VO increased mRNA levels for the fetal genes β-myosin heavy chain and skeletal α-actin and reduced the mRNA level of sarcoplasmic reticulum Ca ²⁺ ATPase. In a myocyte-enriched myocardial fraction, transforming growth factor-β ₃ and insulin-like growth factor-1 mRNA levels were increased with PO but not VO; acidic fibroblast growth factor mRNA was unchanged with PO but decreased with VO. In a nonmyocyte-enriched myocardial fraction, transforming growth factor-β ₃ and insulin-like growth factor-1 mRNA levels were decreased with VO but unchanged with PO. Conclusions PO- and VO-induced LV hypertrophies are associated with distinct molecular phenotypes and patterns of peptide growth factor induction. Stimulus-specific heterogeneity in the signaling events and peptide growth factors coupled to gene expression could play a role in determining the type of hypertrophy that is caused by various forms of hemodynamic overload.