Immunocytochemical study with anti-muscle actin antibody (HHF35) on myocardial ischaemia and reperfusion injury in rats

Sequence and time course of depletion of cardiac cellular proteins and accumulation of plasma proteins in rat early ischemic myocardium

In order to investigate the sequence and time course of fibronectin (Fn), fibrinogen (Fg), complement (C5), myoglobin (Mb), actin (HHF35), and desmin (Dm) for the diagnosis of early myocardial ischemia, the myocardial ischemia model was established in rats, the positive reaction areas of Fn, Fg and C5 and the depletion areas of Mb, HHF35 and Dm in the ischemic cardiomyocytes were studied with immunohistochemistry, image analysis technique and statistical system. The results showed that the depletion of Dm, HHF35 and Mb, and the positive staining of Fg and C5 in ischemic cardiomyocytes were found as early as 15 min after the myocardial ischemia, but the positive staining of Fn occurred till 3 h after myocardial ischemia. With the prolongation of ischemia, the areas of the depletion of Dm, HHF35, Mb and the positive staining of Fg, C5 and Fn gradually enlarged. It is suggested that all the six immunohistochemical markers are more sensitive than routine H&E staining, and that Dm, HHF35, Mb, Fg, C5 are more sensitive markers than Fn for detection of early myocardial ischemia.

Is immunohistochemistry a useful tool in the postmortem recognition of myocardial hypoxia in human tissue with no morphological evidence of necrosis?

Myocytes in the border zone of myocardial infarction are under severe hypoxia without characteristic morphology of necrosis, and show ultrastructural features similar to those seen within the first hours after coronary occlusion. This study was carried out to evaluate the possibility that immunohistochemical methods could be used for the early diagnosis of myocardial infarction by detecting areas of hypoxia. Nineteen human sections of formalin-fixed paraffin-embedded myocardial samples showing a necrotic area and its border were submitted to immunohistochemical staining with the markers antimuscle actin, antimyoglobin, antitroponin T, antifibronectin, and anticomplement component C9. Sections were also subjected to azan trichrome and hematoxylin-basic fuchsin-picric (HBFP) staining techniques. Immunohistochemistry and azan trichrome showed that in the border zone there was a pattern of reaction intermediate between the infarcted area and the normal myocardium. The HBFP failed to distinguish these two areas. In conclusion, immunohistochemistry and azan trichrome can recognize myocardial hypoxia. Because hypoxia is an invariable condition in infarction, these techniques can be used to confirm suspected cases of myocardial infarction in which necrosis is not yet evident. However, considering that agonal states may be associated with generalized hypoxia, further studies are needed to confirm the reliability of this procedure in the earlier phases of myocardial infarction.

Magnesium deficiency in adult rats promotes the induction of ventricular tachycardia by the administration of epinephrine

The effects of magnesium deficiency on epinephrine-induced ventricular tachyarrhythmia were investigated in adult rats. Forty-two adult Wistar rats were fed a magnesium-deficient diet while 30 rats were fed a standard diet for 20 days. The plasma magnesium concentration was lower in the magnesium-deficient rats (0.22+/-0.01 mmol/l) than in the control rats (0.76+/-0.03 mmol/l, P < 0.001). Using a telemetry system, electrocardiograms and arterial blood pressure were recorded on a polygraph in an unrestrained condition. Epinephrine was infused intravenously starting at 5 microg/kg per minute. The QT interval was prolonged to 50+/-1 ms in the magnesium-deficient rats compared with 44+/-1 ms in the control rats (P < 0.001). Before the administration of epinephrine, no ventricular tachyarrhythmias or seizures were found in either the control or the magnesium-deficient rats. The incidence of epinephrine-induced sustained ventricular tachycardia (VT) was higher in the magnesium-deficient rats (86%) than in the control rats (43%, P < 0.01). However, this VT did not result in sudden death. Seizures always preceded death in both the magnesium-deficient and control rats while the arrhythmias observed immediately before death were mainly bradyarrhythmias. The present study in an adult rat magnesium-deficient model revealed that magnesium deficiency enhances the susceptibility to epinephrine-induced ventricular tachyarrhythmias.

Immunohistochemical study of fibronectin for postmortem diagnosis of early myocardial infarction

The postmortem diagnosis of early myocardial infarction has been a puzzling problem in forensic practice. In the present study, an immunohistochemical study of fibronectin (FN) was performed for the first time on 34 autopsy hearts to determine early myocardial infarction with streptavidin/biotin/peroxidase technique. Five cases of definite myocardial infarction showed positive FN staining of cardiomyocytes; of 18 cases where early myocardial infarction was suspected, positive FN staining of cardiomyocytes was found in 15 cases, but no such staining was seen in 11 non-cardiac death controls. The results led to the conclusion that positive FN staining in cardiomyocytes is a reliable marker of acute myocardial infarction and could be used as a new, sensitive method for the postmortem diagnosis of early myocardial infarction. It is worth noting that all cases in this study were autopsied between 8 h and 4 days after death and 5 cases had been fixed in 10% formalin for over 10 years. FN immunohistochemistry still gave satisfactory results in those cases. It seemed that FN was not affected by postmortem autolysis and formalin-fixation and could be used in routine forensic practice, especially for retrospective analysis of cases.