Cardioprotective effect of linseed oil against isoproterenol-induced myocardial infarction in Wistar rats: a biochemical and electrocardiographic study

The present study was designed to evaluate the cardioprotective effect of Tunisian flaxseed oil (Linum usitatissimum) against isoproterenol-induced myocardial infarction in rats by studying hypertensive and cardiac damage markers especially electrocardiographic changes and troponin T serum level. In vitro, the extracted oil showed an important inhibition of angiotensin converting enzyme (ACE) with an IC50 = 85.96 μg/ml. According to chemical analysis, this extract is composed essentially of alpha linolenic acid (ALA), an n-3 polyunsaturated fatty acid (58.59 %). Male rats were randomly divided into three groups, namely control (C), isoproterenol (ISO), and isoproterenol-treated group with flaxseed oil (FO + ISO). Isoproterenol injection showed changes in ECG pattern, including ST-segment elevation (diagnostic of myocardial infarction), increase in the serum levels ofTroponin T and cardiac injury markers (creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), aspartate transaminase (AST), and alanine transaminase (ALT)). However, Linum oil pre-co-treatment prevented almost all the parameters isoproterenol-induced myocardial infarction in rats. Results of the present study proved that flaxseed oil has a significant effect by heart protection against isoproterenol-induced myocardial infarction through beneficial effect of the important fraction of ALA

Different time courses of cardiac contractile proteins after acute myocardial infarction.

For the first time we have compared time courses of cardiac myosin light chain-1 (MLC-1), beta-type myosin heavy chain (MHC), troponin T (TnT), myoglobin, creatine kinase (CK) and CKMB in the same patients with acute myocardial infarction (AMI). Blood samples were serially collected in 23 patients with first-time AMI. All but 3 patients received intravenous thrombolytic treatment. TnT and MLC-1 time courses were biphasic in most patients and showed two distinct peaks in 13 and 8 patients, respectively. MHC time courses were usually monophasic. Only 1 patient showed a biphasic MHC time course with two distinct peak values. Although MHC and MLC were lower by about the fourth day after onset of AMI in early reperfused patients, reperfusion did not qualitatively alter MLC and MHC release (no significant influence on the first appearance in blood or on time to peak). MLC and MHC peaks correlated closely (r = 0.75, P = 0.0001), whereas TnT peaks were correlated less closely with MLC or MHC peaks (r = 0.58 each, P < 0.007). Peak values of all cardiac contractile proteins correlated closely and significantly with CKMB peaks (0.75 < or = r < or = 0.81, P < or = 0.0006). Myoglobin was the first marker to increase in blood after AMI and showed the earliest peaks, whereas MHC increased latest showing the latest peaks. TnT increased significantly (P = 0.0001) earlier than MLC and MHC. These results can be explained by the impact of the intracellular compartmentation of a cardiac protein on the rapidity with which it is released after AMI.

Coexistence of slow and fast isoforms of contractile and regulatory proteins in human skeletal muscle fibres induced by endurance training.

The distribution of fast and slow isoforms of troponin C, I, and T components and myosin heavy chains was investigated in histochemically typed myofibrillar ATPase intermediate (IM) fibres, that is, fibres that stain after both acid and alkaline preincubation in stainings for myofibrillar ATPase. In addition to the previously described IM fibres of types IIC and IB, fibres that displayed staining characteristics between types IIC and IB were observed and termed type IIC-IB. The IM fibres constitute less than 1% of the fibres in normal human limb and abdominal muscles. The IM fibres studied here resulted from extensive endurance training of human triceps brachii muscle (n = 6) and were induced by conversion of a proportion (13%) of type II fibres. The immunohistochemical stains of serial sections with antibodies to slow isoforms of troponin I, T, C and myosin heavy chain showed no staining of type II fibres but intense staining of types I and IB fibres, whereas type IIC fibres stained with intermediate intensity. The antibodies to fast isoforms of the troponin components and myosin heavy chain did not give rise to staining of type I fibres but dark staining of type II fibres. Type IB fibres stained with intermediate intensity and type IIC was either as dark as type II or slightly lighter. Type IIC-IB fibres showed staining intensities intermediate between those observed for types IB and IIC in the immunohistochemical stains. It is therefore concluded that training-induced myofibrillar ATPase intermediate human skeletal muscle fibres are characterized by the coexistence of slow and fast isoforms of contractile and regulatory proteins.(ABSTRACT TRUNCATED AT 250 WORDS)