Effect of diet on increases in systolic pressure induced in rats by chronic cadmium feeding.

Long-term exposure to cadmium in drinking water can induce hypertension in rats. We have consistently observed that from 0.1 to 5 ppm cadmium in deionized drinking water fortified with five essential metals induces a significant pressor effect in female Long-Evans rats on a noncommercial, low cadmium, rye-based diet. To test the effect of diet, a commercial stock diet (Purina Rodent Lab Chow), with either fortified or plain deionized water, was begun at weaning in rats that were receiving water containing 0.1 or 1 ppm cadmium. The overall effect of substituting the stock diet for the rye diet was initially to lessen, and later to prevent entirely, the cadmium-induced pressor effect. Whereas control rats on the rye diet have a constant systolic pressure of about 100 mm Hg throughout the experiment; control rats on the stock diet had an increase in systolic pressure of about 1 mm Hg/month, perhaps because of cadmium from food which contained 10 times as much of the metal as the rye diet. (There was also a somewhat lower pressure among the cadmium-fed rats on stock diet than among those on the rye diet). There were other (non-cadmium) differences between the stock and rye diets and between the remainder of our experimental conditions and those used by other investigators, presumably explaining the failure of some others to induce hypertension with cadmium.