Changes in T-Tubules and Sarcoplasmic Reticulum in Ventricular Myocytes in Early Cardiac Hypertrophy in a Pressure Overload Rat Model

• Main Authors: Perla Pérez-Treviño, Jorge Pérez-Treviño, Cuauhtémoc Borja-Villa, Noemí García, Julio Altamirano
• Format: Article
• Language: English
• Published: Cell Physiol Biochem Press GmbH & Co KG 2015-10-01
• Series: Cellular Physiology and Biochemistry
• Subjects: Transverse tubules; Cardiac hypertrophy; Calcium signaling; Pressure overload; Fluorescence recovery after photobleach; Sarcoplasmic reticulum
• Online Access: http://www.karger.com/Article/FullText/430254

Background/Aims: Pressure-overload (PO) causes cardiac hypertrophy (CH), and eventually leads to heart failure (HF). HF ventricular myocytes present transverse-tubules (TT) loss or disarrangement and decreased sarcoplasmic reticulum (SR) density, and both contribute to altered Ca2+ signaling and heart dysfunction. It has been shown that TT remodeling precedes HF, however, it is unknown whether SR structural and functional remodeling also starts early in CH. Methods: Using confocal microscopy, we assessed TT (with Di-8-ANNEPS) and SR (with SR-trapped Mag-Fluo-4) densities, as well as SR fluorophore diffusion (fluorescence recovery after photobleach; FRAP), cytosolic Ca2+ signaling and ex vivo cardiac performance in a PO rat hypertrophy model induced by abdominal aortic constriction (at 6 weeks). Results: Rats developed CH, while cardiac performance, basal and upon β-adrenergic stimulation, remained unaltered. TT density decreased by ∼14%, without spatial disarrangement, while SR density decreased by ∼7%. More important, FRAP was ∼30% slower, but with similar maximum recovery, suggesting decreased SR interconnectivity. Systolic and diastolic Ca2+ signaling and SR Ca2+ content were unaltered. Conclusion: SR remodeling is an early CH event, similar to TT remodeling, appearing during compensated hypertrophy. Nevertheless, myocytes can withstand those moderate structural changes in SR and TT, preserving normal Ca2+ signaling and contractility.