Abstract 12430: Myofilament Phosphorylation and Function of Diastolic Heart Failure Myocardium: Similarities and Differences Between Beating Heart Biopsies and Postmortem Tissue
Diastolic heart failure (DHF) is a major cause of morbidity and mortality. The main pathophysiological alterations in DHF are increased left ventricular (LV) stiffness and abnormal relaxation, resulting in impaired LV filling. In the present study we aimed to compare alterations in phosphorylation and function of sarcomeric proteins in DHF vs. normal myocardium under two different conditions of tissue procurement: beating heart biopsy and postmortem tissue sampling. LV tissue samples were procured from normal (CTRL) or old dogs made hypertensive by renal wrapping (OHT), either by taking biopsies of the beating heart(n=7/group) or by excising tissue postmortem(n=8/group). Isolated permeabilized cardiomyocytes were attached to a force transducer and passive tension (Fpas) was measured between 1.8 and 2.4µm sarcomere length. Ca2+sensitivity (pCa50) was measured at 2.2µm. Phosphorylation of myofilament proteins was assessed by gel electrophoresis (SYPRO Ruby and ProQ Diamond stain), expression of total and phosphorylated (p) proteins: titin PEVK, TnI, and PKCα by immunoblot. Postmortem tissue and biopsy samples showed similar changes in terms of increased Fpas, pPEVK,and pPKCα expression, and decreased phosphorylation of total titin, MyBPC, TnT, TnI and TnI at Ser23/24, in OHT compared to CTRL. Differences were apparent in terms of lowered pCa50 in postmortem OHT, but increased pCa50 in biopsy OHT. Other differences were low MLC2 phosphorylation and high desmin phosphorylation in OHT compared to CTRL in biopsies, but no change of these parameters in postmortem tissues. Titin degradation form T2 was more abundant in postmortem tissues compared to biopsies. Dog DHF is characterized in both postmortem tissues and beating heart biopsies by titin isoform shift, total titin phosphorylation deficit, high Fpas, increased titin PEVK phosphorylation, and altered pCa50. Differences in some parameters observed between postmortem tissues and biopsies suggest the events associated with death (e.g., catecholamine surge, enzyme dysfunction) can quickly imbalance cardiac protein phosphorylation and function. Using samples from the beating heart is preferable over using postmortem tissue. Data obtained from the latter are to be interpreted with great care.
- © 2011 by American Heart Association, Inc.