en Effects of Low Level of Lead Exposure on Responsiveness of The Rat Isolated Heart to Adrenergics عمومى General پژوهشي Research <span style="font-weight: bold">Background:</span> There are controversial reports about the exact mechanisms of lead-induced hypertension, but many factors such as alteration in the responsiveness of cardiovascular system to endogenous substances including catecholamines could be one of the mechanisms involved. In present study, the effect of exposure to 100 ppm lead acetate by drinking water (in the periods of 4, 8 and 12 weeks) on the responsiveness of rat isolated beating heart to β-adrenergics was investigated, using Langendorff isolated heart setup. <br><span style="font-weight: bold">Methods:</span> The isolated hearts were perfused with Krebs-Henseleit solution at 37˚C and pH=7.4 and gassed with 95% O2 + 5% CO2. The rate (chronotropic) and contractile (inotropic) responses of the heart to β-adrenergics (isoproterenol and dobutamine) were recorded by adding these agents at multiple concentrations to the perfusion solution. <br><span style="font-weight: bold">Results:</span> The blood pressure in 8- and 12-week lead-treated groups was significantly increased compared with those of the control group (P<0.01). The chronotropic response to many doses of isoproterenol (as β1,2-adrenergic) in only 12-, but not in 4- and 8-week lead-treated groups was significantly increased, as compared with those of control (P<0.05). The inotropic response to this drug was also significantly increased in both 8- and 12-week lead-treated rats (P<0.05, P<0.01). Similar findings were observed in the dobutamine (as selective β1-adrenergic) treated groups, but the contractile response of the latter agent was greater than the isoproterenol. <br><span style="font-weight: bold">Conclusions</span>: Low-level of lead increases blood pressure and both chronotropic and inotropic effects of β-adrenergics. These effects could imply an important role in the pathogenesis of lead-induced hypertension. Adrenergic System, Contractility, Hypertension, Lead Acetate Adrenergic System, Contractility, Hypertension, Lead Acetate 254 259 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-2-36&slc_lang=en&sid=1 Reza Badalzadeh رضا بدل زاده reza.badalzadeh@gmail.com 10031947532846003308 10031947532846003308 Yes Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Ali Norouzzadeh علی نوروز زاده 10031947532846003309 10031947532846003309 No Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Mustafa Mohammadi مصطفی محمدی 10031947532846003310 10031947532846003310 No Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Alireza Asgari علیرضا عسگری 10031947532846003311 10031947532846003311 No Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Ali Khoshbaten علی خوش باطن 10031947532846003312 10031947532846003312 No Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran Department of physiology and Biophysics, Medical Faculty, Baqiyatallah University of Medical Sciences,Tehran-Iran