Effects of dietary Ca²⁺ on erythrocyte Na⁺-transport systems in spontaneously hypertensive rats

1. The purpose of this study was to determine the effect of dietary Ca²⁺ intake on blood pressure and erythrocyte Na⁺ transport in spontaneously hypertensive rats.

2. Spontaneously hypertensive rats and Wistar-Kyoto rats were fed diets with three different Ca²⁺ contents, 0.1% (low-Ca²⁺ diet), 0.6% (normal-Ca²⁺ diet) and 4.0% (high-Ca²⁺ diet), between 6 and 20 weeks of age. At 20 weeks of age, the levels of erythrocyte Na⁺ efflux, as well as Na⁺ and K⁺ contents in erythrocytes, were measured.

3. On the low-Ca²⁺ diet, spontaneously hypertensive rats showed an enhancement of hypertension. Conversely, on the high-Ca²⁺ diet, they showed an attenuation of the increase in blood pressure. Spontaneously hypertensive rats had a lower erythrocyte Na⁺ content and increased activity of the Na⁺ pump at higher levels of dietary Ca²⁺. Passive Na⁺ permeability and Na⁺-K⁺ co-transport were similar in spontaneously hypertensive rats on the low-, normal- and high-Ca²⁺ diets. There were no significant differences in blood pressure and in Na⁺ pump activity in WKY on the three different diets.

4. It is concluded that dietary Ca²⁺ might affect the regulation of blood pressure in spontaneously hypertensive rats by changing the activity of Na⁺ pump in the cell membrane.