Dynamics of creatine kinase shuttle enzymes in the human heart

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Abstract
Myocardial cytoplasmic creatine kinase subunits M and B, mitochondrial CK (CKMIT), and citrate synthase (CS) were determined in 10 locations of the normal human heart (n= 8) and in papillary muscles of patients operated on for mitral regurgitation (n= 6). Compared to atrial biopsies, septal and left ventricular biopsies showed higher activities for CS(P < 0.0001), total CK (P < 0.05) and CKMIT (P < 0.0001). CKM was evenly distributed. CKB activity in the right septum and left ventricular locations were 0.5‐1% of total CK and 4–5 times lower than those of the atria and the right ventricular free wall. Activities of CS, CKB and CKMIT in right septal biopsies did not differ from those in left ventricular locations. The activities of CS, total CK, and CKM in papillary muscle from patients operated on for mitral regurgitation did not differ from that of healthy papillary muscle. CKMIT was about 40% lower (P < 0.02), whereas CKB was 15–20 times higher (P < 0.0001) than in the healthy heart. In conclusion, adaptations within the creatine kinase system occur in the human heart in health and disease. Small amounts of CKB in the normal left ventricle, as opposed to the right ventricular free wall, might be related to differences in myocardial perfusion during the cardiac cycle. In disease, a decreased CKMIT and dramatically increased CKB may indicate a stressed intracellular energy transfer. CK enzyme activities in right septal biopsy specimens may be used as an indication of metabolic stress on the myocardium of the left ventricle. Acute myocardial infarction in patients with a healthy heart might not give rise to increased serum CKMB levels.

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