부산대학교 도서관

Interaction between creatine kinase (CK), adenylate kinase (AK) and glycolytic enzymes mediates intracellular high-energy phosphotransfer. While a reduction in CK activity is characteristic of the failing heart, little is known about the potential for compensatory changes in AK and glycolytic enzymes, with no published data for the failing murine heart. The aim of this study was to measure activity of these key phosphotransfer enzymes in two common mouse models of chronic heart failure (CHF). C57BL/6 mice were subjected to transverse aortic constriction (TAC; n = 12), myocardial infarction induced by coronary artery ligation (CAL; n = 15), or sham operation (n = 8-12). Cardiac function was characterised 5-8 weeks post-surgery by echocardiography, left ventricular (LV) haemodynamics assessment and cine-MRI. Mice were selected for the presence of congestive heart failure. Activities of phosphotransfer enzymes CK, AK and glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 3-phosphoglycerate kinase (PGK) and pyruvate kinase (PK) were assessed in LV tissue extracts spectrophotometrically. Western blotting was used for the detection of the total protein LV expression of the predominant AK isoform AK1. All mice had severe LV hypertrophy (LV weight TAC 172% of sham, CAL 132% of sham; p < 0.01), impaired systolic function (fractional area change TAC 33% vs. 59% sham; p < 0.01, ejection fraction CAL 19% vs. 66% sham; p < 0.01) and pulmonary congestion (TAC 120%, CAL 61% increase in lung weight/body weight; p < 0.01) compared to sham controls. A significant decrease in myocardial CK (TAC 5.6 ± 1.2 vs. sham 6.8 ± 0.9 U/mg; CAL 4.5 ± 0.9 vs. sham 5.6 ± 0.8 U/mg p < 0.05) and maximal CK reaction velocity (TAC 345.4 ± 69 vs. sham 490.8 ± 102 p < 0.001; CAL 260.3 ± 67 vs. sham 374.8 ± 45, p < 0.05) was observed in both experimental models. However, despite a significant reduction in AK1 protein expression in both CHF groups (TAC 51%, CAL 39% vs. sham; p < 0.05), the activity of AK (TAC 2.8 ± 0.5 vs. sham 2.6 ± 0.5 U/mg; CAL 2.5 ± 0.5 vs. sham 2.4 ± 0.8 U/mg) and its isoforms (AK1 TAC 2.1 ± 0.5 vs. sham 2.1 ± 0.5 U/mg; CAL 1.6 ± 0.4 vs. sham 1.6 ± 0.4 U/mg) remained unchanged. In contrast, the activities of glycolytic phosphotransfer mediators GAPDH and PGK were 19% and 12% higher in TAC (p < 0.05) and 31% and 23% higher in CAL models (p < 0.05). In conclusion, murine CHF is characterised by impaired CK function, unaltered AK activity, and increased activity of glycolytic phosphotransfer enzymes, independent of CHF aetiology. These results support the concept of increased contribution to phosphotransfer by alternative non-CK pathways during cardiac failure.