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 Ca 2+ 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 Ca 2+ contents, 0.1% (low-Ca 2+ diet), 0.6% (normal-Ca 2+ diet) and 4.0% (high-Ca 2+ 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-Ca 2+ diet, spontaneously hypertensive rats showed an enhancement of hypertension. Conversely, on the high-Ca 2+ 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 Ca 2+ . Passive Na + permeability and Na + -K + co-transport were similar in spontaneously hypertensive rats on the low-, normal- and high-Ca 2+ 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 Ca 2+ might affect the regulation of blood pressure in spontaneously hypertensive rats by changing the activity of Na + pump in the cell membrane.