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| Year : 1981 | Volume
: 27
| Issue : 1 | Page : 16-9 |
Clofibrate, fibrinolysis and experimental myocardial damage.
Saxena KK, Gupta BB, Srivastava RK, Singh RC, Prasad DN
How to cite this article:
Saxena K K, Gupta B B, Srivastava R K, Singh R C, Prasad D N. Clofibrate, fibrinolysis and experimental myocardial damage. J Postgrad Med 1981;27:16 |
How to cite this URL:
Saxena K K, Gupta B B, Srivastava R K, Singh R C, Prasad D N. Clofibrate, fibrinolysis and experimental myocardial damage. J Postgrad Med [serial online] 1981 [cited 2023 Oct 2];27:16. Available from: https://www.jpgmonline.com/text.asp?1981/27/1/16/5669 |
Clofibrate, a well known hypolipidaemic agent has drawn attention for over a past few years with regard to its efficacy in coronary artery disease. It has been shown to exert protective influence against the gross morbid effects in experimental myocardial infarction,[20] development of new infarction and sudden death in clinical cases.[2], [7], [10] Furthermore, it has recently been reported to reduce incidence and severity of arteriosclerosis,[6], [20] an important risk factor in precipitating myocardial infarction. However, the enthusiasm for prophylactic use of clofibrate has received a major setback following a five year U.S. multicenter study report regarding failure of clofibrate in reducing or preventing mortality in cardiovascular disorders.[19]
In view of the fact that altered fibrinolytic activity and plasma fibrinogen prevail following myocardial damage[4], [13], [14]. [16] and clofibrate influences fibrinolytic system[3], [5], [18] the present investigation was envisaged to explore its beneficial effects on fibrinolytic system in association with drug induced myocardial necrosis in rats.
Male Porter strain rats weighing 260 + 8 g were divided in four groups of ten animals each. Animals were fed on commercial rat diet and water was allowed ad libitum during the test period. Two groups of rats were fed clofibrate (100 mg/kg, suspended in 2% gum acacia, orally once daily) for seven consecutive days and the remaining two groups received matching volume of saline. One group each from clofibrate and saline treated animals was challenged with isoprenaline (85 mg/kg, s.c.) on day six and seven. On the eighth day, all the animals were anaesthetized with pentobarbitone sodium (40 mg/kg. i.p.) and blood samples were collected from the abdominal aorta in siliconized glass syringes for estimation of euglobulin clot lysis time (ECLT) I and plasma fibrinogen.[15] Hearts of isoprenaline challenged rats were dissected out and examined gross and microscopically. Cardiac lesions were graded from grade 0 to IV on a five point scale as described by Rona et al.[12]
Results were analysed by employing Student's `t' test and Fisher's exact probability test to calculate the level of significance.
A. Effect of pretreatment with clofibrate on isoprenaline induced myocardial damage:
The distribution of grades of myocardial lesions and number of animals in clofibrate as well as saline pretreated, isoprenaline challenged rats have been depicted in [Fig.1]. As the data obtained do not conform to a normal distribution curve, Fisher's exact probability test was applied.[17] Grades of myocardial necrosis were divided into two groups arbitrarily; group A containing O, I and II grades and group B, III and IV grades. Number of animals in group A and B of clofibrate treated rats were then compared with saline receiving rats. Clofibrate provided significant (p < 0.05) protection from development of myocardial necrosis.
B. Effect of pretreatment with clofibrate on euglobidin clot lysis time (ECLT) and plasma fibrinogen (PF) in normal as well as isoprenaline challenged rats:
The results obtained have been summarized in [Table 1]. Clofibrate per se did not produce any significant alteration in ECLT or PF. Isoprenaline challenge produced marked (p < 0.001) rise in ECLT' and PF while pretreatment with clofibrate in such animals partially prevented this increase in ECLT and PF significantly (p <0.001 and <0.001 respectively) .
Effect of clofibrate on fibrinolytic activity has been a matter of dispute.[3], [5], [18] In the present study, however, clofibrate per se did not exhibit any significant effect on fibrinolytic system as ECLT and PF remained unaltered [Table 1]. These findings are in agreement with those of Sweet et al.[18] Concomitant with myocardial necrosis, the massive doses of isoprenaline exhibited significant diminution in PFA (as evidenced by prolonged ECLT) and rise in PF levels [Table 1]. Interestingly clofibrate pretreatment afforded only partial protection (p < 0.05) to myocardium against isoprenaline induced necrosis. However, Wexler and Greenberg[20] failed to observe histological improvement in cardiac necrosis following isoprenaline challenge.
Results of the present study explicitly indicate that clofibrate significantly prevented the decrease in PFA and increase in PF levels which are inevitable consequences of myocardial infarction.[4], [16] Depression in fibrinolytic activity following myocardial infarction could in part be attributed to the antifibrinolytic property of lipids8 which are known to be raised following myocardial infarction.[11] Antilipaemic action of clofibrate could account for the prevention of the diminution in PFA. Registered improvement in PFA during acute stress of myocardial infarction in clofibrate treated animals, might as well be contributed by the steroids9 which are increased by clofibrate.[20] Since depression of PFA and elevation of PF are the responses of acute myocardial infarction4, [16] and clofibrate is devoid of a per se effect on fibrinolytic system, it will not be unfair to speculate that prevention of changes in PFA and PF are secondary to protection of myocardium from isoprenaline induced damage.
In view of the favourable effects of clofibrate on myocardial necrosis, abnormal PFA and PF, further clinical studies are required to re-evaluate its utility in cardiovascular disorders.
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| 14. | Saxena, K. K., Gupta, B., Srivastava, V. K., Kulshrestha, V. K. and Prasad, D. N.: On the significance of plasma fibrinogen level to assess the severity of myocardial damage-an experimental study. Ind. J. Expt. Biol., 17: 600-602, 1979. |
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