RESUMO
Exposure to high concentrations of cadmium (Cd), widely used in many industries and found in air, food and contaminated water, is not uncommon. Cd damages the cardiovascular system, but the vascular mechanisms involved are not fully understood. This study investigated the mechanisms involved in cardiovascular damage after exposure to high Cd concentrations. Three-month-old male Wistar rats were treated intraperitoneally for 14 days with distilled water (Untreated group) or 1â¯mg/kg cadmium chloride (Cd group). We investigated the systolic blood pressure (SBP) and vascular reactivity of mesenteric resistance arteries (MRA) and the aorta by analysing contractile and relaxation responses in the absence and presence of the endothelium; we also evaluated pathways involved in vascular tone regulation. Superoxide anion production, COX-2 protein expression and in situ detection of COX-2, AT-1, and NOX-1 were evaluated. Oxidative status, creatinine level and angiotensin-converting enzyme (ACE) activity in plasma were also evaluated. Fourteen-day exposure to a high Cd concentration induced hypertension associated with vascular dysfunction in MRA and the aorta. In both vessels, there was increased participation of cyclooxygenase 2 (COX2), angiotensin II type 1 (AT1) receptor and NOX1. MRA also presented endothelial dysfunction, denoted by impaired acetylcholine-mediated relaxation. All vascular changes were accompanied by increased reactive oxygen species production and COX2, NOX1 and AT1 receptor expression in vascular tissue. Overall, high Cd concentrations induced cardiovascular damage: hypertension, endothelial dysfunction and vascular damage in conductance and resistance arteries, NADPH oxidase, renin-angiotensin system and COX2 pathway activation.
Assuntos
Cloreto de Cádmio/toxicidade , Ciclo-Oxigenase 2/metabolismo , Endotélio Vascular/efeitos dos fármacos , Poluentes Ambientais/toxicidade , Hipertensão/induzido quimicamente , NADPH Oxidases/metabolismo , Sistema Renina-Angiotensina/efeitos dos fármacos , Animais , Aorta/efeitos dos fármacos , Aorta/enzimologia , Pressão Sanguínea/efeitos dos fármacos , Cloreto de Cádmio/sangue , Relação Dose-Resposta a Droga , Endotélio Vascular/enzimologia , Endotélio Vascular/patologia , Endotélio Vascular/fisiopatologia , Poluentes Ambientais/sangue , Hipertensão/enzimologia , Hipertensão/patologia , Hipertensão/fisiopatologia , Injeções Intraperitoneais , Masculino , Artérias Mesentéricas/efeitos dos fármacos , Artérias Mesentéricas/enzimologia , Estresse Oxidativo/efeitos dos fármacos , Ratos Wistar , Transdução de Sinais , Vasoconstrição/efeitos dos fármacosRESUMO
Cadmium exposure induces low birth weight through unknown mechanisms. Since low birth weight is associated to foetal exposure to high glucocorticoids (GC) concentrations, we hypothesized that low birth weight induced by prenatal exposure to Cd(2+) is, at least in part, mediated by higher foetal exposure to GC, specifically corticosterone, the main active GC in rodents. Pregnant rats were exposed to different dose of CdCl(2) administered in drinking water during the whole pregnancy period. At term, corticosterone was measured by enzyme immunoassay in maternal and foetal blood and in placental tissues. Cadmium was determined in placentas, maternal tissues (liver and kidney) and foetuses by inductively coupled plasma-mass spectrometry (ICP-MS). Placental 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) activity and expression were determined by a radiometric conversion assay and quantitative RT-PCR respectively. Results demonstrated that 50 ppm of Cd(2+), which was accumulated in different maternal tissues but not in the foetus, reduced pup birth weights and increased plasma corticosterone concentrations, both in mother and foetus. Placental 11beta-HSD2 activity and expression did not change by the treatment. We conclude that 50 ppm of Cd(2+) administered during pregnancy, increase foetal corticosterone concentrations due, probably, to alterations of the regulatory mechanisms of placental barrier to GC causing a mild but significant reduced birth weight.