Effect of Dietary Calcium Supplements and Amlodipine on Growth,Arterial Blood Pressure,and Cardiac Hypertrophy of Spontaneously Hypertensive Rats

It has been shown that calcium‐enriched diets cause a decrease in arterial blood pressure in hypertensive patients and animals. Moreover, it has been suggested that the combination of dietary calcium and calcium antagonists could paradoxically have a synergistic effect in order to decrease arterial blood pressure. The combination of these treatments may also have potential therapeutic benefit in the attenuation of cardiac hypertrophy. In this study, after being weaned at three weeks, male spontaneously hypertensive rats (SHR) were randomized in four groups of animals. Two of these groups were fed on a normal calcium diet (Ca 1%) and another two groups were fed on a calcium‐enriched diet (Ca 2.5%). One of the groups fed on each diet also received amlodipine (1 mg/kg/day) in the drinking water after being weaned. Body weight was measured weekly in all the groups, and arterial blood pressure was also measured in all the 10‐, 15‐, 20‐, and 25‐week‐old SHR by the tail cuff method. We established the ratio heart weight/body weight × 1000 (R), and we weighed the left ventricle in the 25‐week‐old animals at the end of the different treatments. The Ca 2.5% diet caused a delay in the development of hypertension in SHR. This effect could not be correlated with alterations in body weight since this diet improved growth in these rats. Amlodipine did not alter growth in SHR. This pharmacological treatment caused a decrease in the arterial blood pressure of the SHR and it intensified the antihypertensive effect of the Ca 2.5% diet. Nevertheless, this drug attenuated the effect of dietary calcium on body weight and when the treatment was prolonged, almodipine also antagonized the effect of dietary calcium on arterial blood pressure. At the end of the different treatments the ratio R and the left ventricular weight were similar in all the groups of animals. Therefore, the use of dietary calcium with a calcium antagonist to control arterial blood pressure seems not to be advisable, and the present data do not prove the usefulness of the mentioned antihypertensive treatments in preventing cardiac hypertrophy.