Effects of Low-Level Cadmium Intake on the Contractility and Morphology of the Rat Aorta

Abstract

Female Long Evans hooded rats with an initial mean (± SE) weight of 85.7 ± 1.2 g were exposed to 5 ppm cadmium (Cd) in drinking water for 6 months. Rats which received no Cd in the drinking water served as untreated controls. Weights, systolic blood pressures (tail cuff method), several aspects of aortic ultrastructure, and isolated aortic contractile responses to epinephrine, angiotensin, and potassium chloride at 0, 1, 2, 3, and 6 months were observed in both groups. At none of the testing times was there a significant difference between the weights or systolic blood pressures of the control and Cd-treated groups. Analysis of variance indicated that aortas from control and Cd-treated rats showed similar age-related changes in maximum tension development (contractility) and similar threshold doses. However, Cd-treated aortas developed significantly less maximum tension than control aortas when compared at the same time intervals in response to all of the vasoconstrictors tested. This decreased contractility was apparent at one month and persisted at about the same level (20%) at 2, 3, and 6 months. There were also expected age-related changes in aortic ultrastructure of both groups, and although the 6-month Cd-treated aortas showed more degenerating endothelial cells, differences that might explain the consistent decreases in contractility of the Cd-treated aortas were not observed. The results of this study indicate that chronic low-level Cd treatment causes decreases in aortic contractility, as have previously been reported for acute exposure to Cd, but that this change is not associated with the development of hypertension or with structural changes in the aorta.