ABSTRACT
The heart maintains a 10,000-fold gradient between the extracellular calcium concentration, which is in the millimolar range and intracellular calcium concentration, which is in the nanomolar range. Elevated cytosolic calcium concentrations have been shown in spontaneous and oscillatory release of calcium from the sarcoplasmic reticulum. Smooth muscle cells maintain the same calcium concentration gradient across the sarcolemma, with a small change in intracellular calcium concentration resulting in striking changes in cell function. In the elderly, a diet consisting of an excess of calories, saturated fat, cholesterol or salt and one deficient in the potassium, the calcium and the magnesium is thought to contribute to the incidence of hypertension. The observation that humans living in areas with “hard” water, i.e., high in calcium, had a lower incidence of heart disease sparked studies into the relationship between the calcium intake and the blood pressure.
