Influence of hypertension and dietary copper on indexes of copper status in rats.

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Abstract
The Dahl salt-sensitive rat was used to investigate the effect of hypertension on indexes of copper status and to determine the extent to which dietary manipulation of copper attenuated, or exacerbated, the rate of sodium chloride-induced hypertension. Weanling salt-sensitive rats were fed, in a 2 x 3 factorial design, one of six diets that contained one of three levels of copper (2.0 micrograms/g marginal, 12 micrograms/g adequate, or 50 micrograms/g supplemental) and either control (0.4%) or high (4%) levels of sodium. Diets were fed to the rats for 11 weeks. Rats fed the high sodium diets were characterized by high plasma copper concentrations and ceruloplasmin activities compared with their respective control sodium rats. The magnitude of the sodium-induced rise in plasma copper and ceruloplasmin was affected by dietary copper intake; however, dietary copper intake had no effect on the development of hypertension in the high sodium groups. These results suggest that altered copper metabolism is secondary, rather than primary, to the development of sodium chloride-induced hypertension in the salt-sensitive rat. Red blood cell superoxide dismutase activity was reduced in rats fed the low copper diets compared with the adequate and supplemented copper groups. At the lower levels of copper intake, sodium chloride-induced hypertension increased red blood cell superoxide dismutase activity in a manner consistent with the plasma copper and ceruloplasmin changes observed. However, at adequate or supplemental levels of dietary copper, red blood cell superoxide dismutase activity plateaued, suggesting possible saturation of copper at sites of hematopoeisis.