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Indian Journal of Pharmacology, Vol. 39, No. 5, September-October, 2007, pp. 249-250 Research Letter Positive inotropic and chronotropic effect of aloe gel on isolated rat heart Pradeep Kumar, Manish Goyal, Sunita Tewari Department of Physiology, K.G. Medical University, Lucknow Correspondence Address:Department of Physiology, K.G. Medical University, Lucknow Code Number: ph07062 Aloe vera ( Aloe barbadenesis ), an indigenous medicinal plant [1] of family Liliaceae, is widely distributed in Asia, Africa and other tropical areas. It has been used in folk medicine for the treatment of skin ailments, including burns and wound healing. [2] It has lipid lowering [3] and hypotensive [4] actions and also reduces the frequency of anginal attacks. [5] A recent study has reported that aloe is a strong antioxidant and has free radical scavenging properties. [6] We hypothesized that aloe contains some cardioactive substance. To the best of our knowledge, the effect of aloe on isolated heart preparation has not been investigated. The objective of this study was to elucidate the effect of aloe on isolated heart. An aqueous solution of aloe was prepared by taking 1 gm of gel from the leaf of the aloe plant and dissolving it in 10 ml of distilled water; this solution was centrifuged at 3000 rpm for 15 min and the supernatant was filtered and used for the study. The Institutional Ethics Committee approved the study and all efforts were made to minimize animal suffering and to reduce the number of animal used. A total of 12 albino rats (150-200 gm), procured from Central Drug Research Institute (CDRI), Lucknow, were randomly divided into two groups (control and experimental) of six rats each. The animals were anaesthetized with thiopental sodium, 25 mg/kg body weight, intraperitonially. Hearts were exposed through a left thoracotomy and the pericardium was removed. Heparin (1000 IU) was injected into the ventricles and the hearts were quickly removed and placed in ice-cold Krebs-Henseleits solution of pH 7.4, containing NaCl (118.0 mmol/l), KCl (4.7 mmol/l), CaCl 2 (2.5 mmol/l), MgSO 4 (1.0 mmol/l), KH 2 PO 4 (1.0 mmol/l), glucose (11.0 mmol/l) and NaHCO 3 (25.0 mmol/l). The hearts were thoroughly washed with ice-cold Kreb′s solution and then perfused according to non-recirculating Langendroff technique. Kreb′s solution, equilibrated with 95% O 2 + 5% CO 2 , was delivered through an aortic cannula at 37°C under a constant pressure of 60 mm Hg. Following perfusion, the hearts started beating spontaneously. All the hearts were perfused for 15 min to allow stabilization. Basal heart rate, the rate after each intervention and the force of contraction were recorded on a physiograph (Bio Device, Ambala, India); coronary flow per minute was recorded by collecting the coronary effluent. The hearts of the experimental group were perfused with an aqueous solution of Aloe in doses of 100 mg, 200 mg and 300 mg per liter of Kreb′s solution. The hearts were perfused with Kreb′s solution to wash the preparation after each intervention. Propranolol (1 µmol/l) was infused with Kreb′s solution in both groups and aloe solution, 300 mg/l, was infused in the experimental group. Data were analyzed using Student′s t test; P < 0.05 was taken as indicating a significant difference. Observation showed that in the aqueous solution, aloe at a dosage of 200 mg/l and 300 mg/l of Kreb′s solution significantly ( P < 0.01) increased the heart rate, force of contraction and coronary flow in the hearts of the experimental group and the effect persisted during the continuous infusion over 10 min. Aloe vera at a dose of 100 mg/l did not show any effect ( P > 0.05); aloe at a dose of 300 mg/l, when administered along with propranolol (10 -6 mol/l), did not show any significant effect. In the present study, the increase in the hemodynamic parameters is associated with aloe vera infusion and is dose dependant [Table 1]. In the isolated heart preparation, increase in heart rate and force of contraction is due to sympathetic discharge of noradrenalin [7] and the effect is mediated via β2 receptors in the myocardium. In our study, the effect is blocked by propranolol, which suggests that the active ingredient present in aloe vera may be acting either on the β-receptors or any other receptors that are blocked by propranolol. Further research is needed to rule out the possibility that the aloe solution could be responsible for stimulation of sympathetic nerve endings present in the myocardium. In the coronary arteries β-adrenergic receptors mediate vasodilatation. Activity in the noradrenergic nerves to the heart and injection of norepinephrine causes coronary vasodilatation. In our study it seems that increase in coronary flow is either due to accumulation of metabolites that may cause coronary vasodilatation or due to some substance present in aloe vera acting on β-adrenergic receptors. The active ingredients in aloe gel are amino acids, enzymes, minerals, vitamins and glycoside (saponins). [8] With this preliminary study, we are not able to identify the ingredients which is responsible for the positive inotropic and chronotropic effect on isolated heart. Aloe vera is reported to be useful in wound healing, asthma and anginal attacks and has lipid lowering, hypotensive and antioxidants properties. [2],[3],[4],[5],[6] References
Copyright 2007 - Indian Journal of Pharmacology The following images related to this document are available:Photo images[ph07062t1.jpg] |
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![[Table 1]](/showimage?ph/photo/ph07062t1.jpg){kind=link}