Myocardial tissue troponins T and I. An immunohistochemical study in experimental models of myocardial ischemia.
BACKGROUND
Cardiac troponins T (cTnT) and I (cTnI) are proven diagnostic and risk stratification biomarkers in patients with acute coronary syndromes. To date, no immunohistochemical studies have been performed which allow visualization of the time course and pattern of myocardial troponin egress from the myocardium during the early evolution of ischemic injury in experimental systems.


METHODS
We studied archival formalin-fixed, paraffin-embedded myocardium from 50 experimental animals (dogs, pigs and rats) that had undergone permanent coronary occlusion (n = 34) for 0.5-6 h or occlusion of 0.75-6 h followed by reperfusion (n = 16). Histologic sections that included ischemic and nonischemic myocardium were studied by immunohistochemistry with three different antibodies to human cTnI and one to cTnT, using a standard avidin-biotin-peroxidase system.


RESULTS
All antibodies detected cTnT or cTnI in normal myocardium and its loss from necrotic myocardium, in some cases as early as 30 min after coronary occlusion, before histologic evidence of necrosis was present. Loss was nonuniform, being greater at the periphery of the infarcts then at their central regions. Usually, loss of cTnT appeared greater than loss of cTnI. With reperfusion, findings were similar to those after permanent occlusion, except that there was a greater contrast between loss at the periphery compared to the loss in the central region. Considerable residual staining persisted for hours after occlusion, indicating delayed release over time, concordant with sustained serum elevations in patients with acute myocardial infarction. No loss of staining was observed in nonnecrotic myocardium.


CONCLUSIONS
Immunohistochemical staining using antibodies to human cTnT and cTnI can be used to visualize cardiac troponins and document their loss in histologic sections of myocardium in different animal species. Loss of cTnT and cTnI occurs very early following ischemic injury and may precede histologic evidence of necrosis, but does not occur in myocardium that is not necrotic. Immunohistochemical staining of hearts for cTnT and cTnI can assist in the often difficult recognition of myocardial necrosis at autopsy, in patients suspected of dying from acute myocardial ischemia.
Fishbein
Michael C
MC
Division of Anatomic Pathology, Department of Pathology and Laboratory Medicine, UCLA Center for the Health Sciences, A7-149 CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095-1732, USA. mfishbein@mednet.ucla.edu
Wang
Tiffany
T
Matijasevic
Maria
M
Hong
Longsheng
L
Apple
Fred S
FS
D000818:Animals; D000830:Animals, Laboratory; D015415:Biomarkers / Q000032:analysis; D004195:Disease Models, Animal; D004285:Dogs; D007124:Immunoenzyme Techniques; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D009336:Necrosis; D051381:Rats; D013552:Swine; D013997:Time Factors; D019210:Troponin I / Q000032:analysis / Q000378:metabolism*; D020107:Troponin T / Q000032:analysis / Q000378:metabolism*
D015415:Biomarkers; D019210:Troponin I; D020107:Troponin T