Discrimination between myocardial and skeletal muscle injury by assessment of the plasma ratio of myoglobin over fatty acid-binding protein.
BACKGROUND
Myoglobin and fatty acid-binding protein (FABP) each are useful as early biochemical markers of muscle injury. We studied whether the ratio of myoglobin over FABP in plasma can be used to distinguish myocardial from skeletal muscle injury.


RESULTS
Myoglobin and FABP were assayed immunochemically in tissue samples of human heart and skeletal muscle and in serial plasma samples from 22 patients with acute myocardial infarction (AMI), from 9 patients undergoing aortic surgery (causing injury of skeletal muscles), and from 10 patients undergoing cardiac surgery. In human heart tissue, the myoglobin/FABP ratio was 4.5 and in skeletal muscles varied from 21 to 73. After AMI, the plasma concentrations of both proteins were elevated between approximately 1 and 15 to 20 hours after the onset of symptoms. In this period, the myoglobin/FABP ratio was constant both in subgroups of patients receiving and those not receiving thrombolytics and amounted to 5.3 +/- 1.2 (SD). In serum from aortic surgery patients, both proteins were elevated between 6 and 24 hours after surgery; the myoglobin/FABP ratio was 45 +/- 22 (SD), which is significantly different from plasma values in AMI patients (P < .001). In patients with cardiac surgery, the ratio increased from 11.3 +/- 4.7 to 32.1 +/- 13.6 (SD) during 24 hours after surgery, indicating more rapid release of protein from injured myocardium than from skeletal muscles.


CONCLUSIONS
The ratio of the concentrations of myoglobin over FABP in plasma from patients with muscle injury reflects the ratio found in the affected tissue. Since this ratio is different between heart (4.5) and skeletal muscle (20 to 70), its assessment in plasma allows the discrimination between myocardial and skeletal muscle injury in humans.
Van Nieuwenhoven
F A
FA
Department of Physiology, University of Limburg, Maastricht, The Netherlands.
Kleine
A H
AH
Wodzig
W H
WH
Hermens
W T
WT
Kragten
H A
HA
Maessen
J G
JG
Punt
C D
CD
Van Dieijen
M P
MP
Van der Vusse
G J
GJ
Glatz
J F
JF
D000368:Aged; D001012:Aorta, Abdominal / Q000601:surgery; D002352:Carrier Proteins / Q000032:analysis / Q000097:blood*; D016022:Case-Control Studies; D001026:Coronary Artery Bypass; D004797:Enzyme-Linked Immunosorbent Assay; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use; D006350:Heart Valve Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000737:chemistry / Q000293:injuries*; D018996:Myelin P2 Protein / Q000032:analysis / Q000097:blood*; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis* / Q000188:drug therapy; D009206:Myocardium / Q000737:chemistry; D009211:Myoglobin / Q000032:analysis / Q000097:blood*; D009363:Neoplasm Proteins; D013300:Streptokinase / Q000627:therapeutic use; D025521:Tumor Suppressor Proteins
D002352:Carrier Proteins; C107608:FABP7 protein, human; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D005343:Fibrinolytic Agents; D018996:Myelin P2 Protein; D009211:Myoglobin; D009363:Neoplasm Proteins; D025521:Tumor Suppressor Proteins; D013300:Streptokinase