The effects of endothelium removal (E⁻) (A, B) and <i>N</i>^G-nitro-L-arginine methyl ester (L-NAME, 100 µM) (D, E) on the concentration-response curve for phenylephrine treatment in aortic rings from untreated (CT) and lead-treated rats (Pb⁺²).

<p>The inset shows differences in area under the concentration-response curves (dAUC) in endothelium–denuded and intact segments (C) and in the presence and absence of L-NAME (F). Densitometry analyses of western blots for endothelial nitric oxide synthase (eNOS) and phosphorylated endothelial nitric oxide synthase (p-eNOS) protein expression in aortas from untreated (CT) and lead-treated rats (Pb⁺²) (G). Representative blots are also shown. *P<0.05 by Student's <i>t-</i>test. Number of animals used is indicated in parentheses.</p

Angiotensin converting enzyme (ACE) activity (nmol His-Leu/min) in plasma; correlation between systolic arterial blood pressure and ACE activity (nmol His-Leu/min) in plasma of control and lead-treated rats (r = 0.787, P<0.05).

<p>*P<0.05 by Student's <i>t-</i>test. Number of animals used is indicated in parentheses.</p

Potassium-induced relaxation in aortic rings from untreated (CT) and lead-treated (Pb⁺²) rats previously incubated in a K⁺-free medium and contracted with phenylephrine before and after incubation with 100 µM ouabain (A).

<p>Densitometry analyses of the western blots for the alpha-1 subunit (B) and alpha-2 subunit (C) in aortas from untreated (CT) and lead-treated rats (Pb⁺²). Representative blots are also shown. *P<0.05 (CT <i>vs.</i> Pb⁺²) by Student's <i>t-</i>test or two-way ANOVA followed by a Bonferroni test. ^#P<0.05 (CT OUA <i>vs.</i> Pb⁺² OUA) by two-way ANOVA followed by a Bonferroni test. Number of animals used is indicated in parentheses.</p

Changes in arterial pressure.

<p>Changes in systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) before (Ct) and after Hexamethonium (Hexa) administration and following lead exposure (Hexa+Pb). *p<0.05 compared with untreated controls. The number of animals used is indicated in parentheses.</p

The effects of seven-day exposure to lead acetate on the concentration-response curves to phenylephrine (A), acetylcholine (B) and sodium nitroprusside (NSP; C) treatment in aortic rings.

<p>*P<0.05 by Student's <i>t-</i>test. Number of animals used is indicated in parentheses.</p

Changes in arterial pressure.

<p>Changes in systolic arterial pressure-SAP (A and C) and diastolic arterial pressure-DAP (B and D) before (Ct) and after Losartan (Los) or Enalapril (Enal) administration and following lead exposure (Los+Pb; Enal+Pb). A and B show the Losartan protocol; C and D show the Enalapril protocol. *p<0.05 compared with untreated controls. The number of animals used is indicated in parentheses.</p

Effect of losartan (10 µM) (A, B) and enalapril (10 µM) (C, D) on the concentration-response curves to phenylephrine in endothelium-intact aortic segments from untreated (CT) and lead-treated rats (Pb⁺²).

<p>Densitometry analyses of the western blots for receptors AT₁ (E) and AT₂ (F) in aortas from untreated (CT) and lead-treated rats (Pb⁺²). Representative blots are also shown.*P<0.05 by Student's <i>t-</i>test. Number of animals used is indicated in parentheses.</p

Effects of lead on protein expression and ACE activity.

<p>Effects of lead exposure on the protein expression of the (A) AT1 and (B) AT2 receptors and on (C) ACE activity. *p<0.05 compared with untreated controls. The number of animals used is indicated in parentheses.</p

Hemodynamic parameters upon acute lead exposure.

<p>SAP- systolic arterial pressure, DAP- diastolic arterial pressure, HR- heart rate, Ct- Control. The results are expressed as the mean ± SEM.</p><p>*p<0.05 compared with controls (time 0); n = 10.</p

Effects of aminoguanidine, TEA, losartan and enalapril on the vascular responses to phenylephrine (R_max and pD₂) in aortas from untreated and lead-treated rats.

<p>Results are expressed as mean ± SEM of the number of animals shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0017117#pone-0017117-g003" target="_blank">Figs. 3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0017117#pone-0017117-g005" target="_blank">5</a> ; R_max, maximal effect (expressed as a percentage of the maximal response induced by 75 mM KCl); pD₂, −log one-half R_max; AG; aminoguanidine, TEA; tetraethylammonium, losartan, enalapril. P<0.05 <i>vs.</i> untreated control rats (^#) and lead-treated control rats (*).</p