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J.Health Sci., 53(2), 151-155, 2007
α-Adrenergic Receptor Mediated Hypertensive and Vasoconstrictor Effects of Dietary Radish Leaves Extract
Muhammad Nabeel Ghayura, b and Anwarul Hassan Gilani*, a
aDepartment of Biological and Biomedical Sciences, Aga Khan University Medical College, Karachi-74800, Pakistan and
bDepartment of Medicine, McMaster University, St. Joseph's Hospital, Hamilton L8N 4A6, Ontario, Canada
Radish is a universally known food plant. Leaves of radish are widely used for their culinary and medicinal properties. In this study we report the hypertensive and vasoconstrictor effects of the aqueous crude extract of radish leaves (Rl.Cr) mediated possibly via activation of α-adrenergic receptors. Rl.Cr, that tested positive for the presence of saponins and alkaloids, exhibited a dose-dependent (10-300 mg/kg) hypertensive effect in the blood pressure (BP) of rats under anaesthesia. This effect was blocked in the presence of phentolamine (2 mg/kg), similar to norepinephrine (NE) a standard adrenergic agonist. Further investigations were conducted on the isolated tissue preparations. In rabbit aorta, Rl.Cr showed a dose-dependent (0.3-5 mg/ml) vasoconstrictor effect that was sensitive to phentolamine pretreatment. Phentolamine pretreatment also shifted the curves of Rl.Cr in a parallel manner to the right in aorta, similar to NE, thus possibly confirming the adrenergic receptor mediated effect. However, Rl.Cr was devoid of any activity in isolated guinea pig atria up to the dose of 10 mg/ml indicating that the extract has a specific α-adrenergic effect independent of β-adrenergic receptor involvement. Thus the study shows hypertensive and vasoconstrictor activities of radish leaves extract possibly mediated via interaction at α-adrenergic receptors.
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