Unchanged heat-shock protein 70 expression in myocardium of patients with permanent atrial fibrillation.

AIM: Cardiomyocytes respond to permanent atrial fibrillation (AF) with an increase in mitochondrial heat shock proteins (Hsp). The aim of our study was to test if there is a cytoplasmic response to stress by investigating the expression of Hsp70. METHODS: Right atrial samples from 18 patients undergoing elective cardiac surgery were excised and immediately frozen in liquid nitrogen. Eight patients had permanent AF (> 3 months) and 10 patients were in sinus rhythm (SR). Hsp70 was determined by SDS-PAGE, Western blot and quantified with optical densitometry. RESULTS: We found no increase in Hsp70 expression in myocardial samples from patients with permanent AF. CONCLUSION: The unchanged expression of Hsp70 may indicate that the cytoplasmic stress response in permanent AF is exhausted.

Chronic atrial fibrillation: decreased actin expression in patients with chronic atrial fibrillation.

AIM: Chronic atrial fibrillation (AF) is characterized by a severe contractile dysfunction and myolysis, which develops progressively. Myolysis and the remodelling of the cellular ultrastructure is associated with the replacement of sarcomeres by glycogen. The aim of our study was to determine if myolysis is characterized by a reduction in actin concentration. METHODS: Right atrial samples from 18 patients undergoing elective cardiac surgery were excised and immediately frozen in liquid nitrogen. Eight patients had chronic AF (>3 months) and 10 patients were in sinus rhythm (SR). Actin concentration was determined by sodium dodecyl sulfate-polycrylamide gel electrophoresis (SDS-PAGE), Western blot and quantified by optical densitometry. RESULTS: Immunoblot analysis demonstrated actin expression in all hearts. In myocardial samples from patients with chronic AF we found a 2.1 fold reduction in actin expression. (P<0.001) CONCLUSION: The decrease in actin concentration via myolysis, might decrease energy consumption and be an additional mechanism for contractile dysfunction in chronic AF.

Heat shock protein 60 expression in patients undergoing cardiac operations.

AIM: Cardiomyocytes respond to stress with the expression of different heat shock proteins (HSP). The mitochondrial HSP60 is known to be expressed by various stress factors, including ischemia and reperfusion. The aim of this study was to investigate if HSP60 is increased in human myocardium after cardiac surgery. METHODS: To determine if heat shock protein 60 accumulated in the myocardium of patients undergoing car-diac operations, right atrial samples before and after extracorporeal circulation were excised and immediately frozen in liquid nitrogen. PATIENTS: we obtained 10 sequential right atrial specimens from 5 male patients in sinus rhythm undergoing elective cardiac surgery. MEASURES: the HSP60 protein level was determined by SDS-PAGE, Western blot and quantified by optical densitometry according to the immunoreactive bands of actin. RESULTS: The HSP60 concentration was unchanged in hearts after a single episode of hypothermic ischemia and reperfusion. Immunoblot analysis demonstrated HSP60 expression in all hearts. There was no correlation with the endurance of cardiopulmonary bypass or reperfusion time. CONCLUSION: These findings indicate that myocardial HSP60 of patients undergoing cardiac operations is not increased after an obligatory period of ischemia, cardioplegic arrest and reperfusion. This might reflect an effective cardioprotection during ECC.