DIETARY CALCIUM, DEFECTIVE CELLULAR CA2-PRESSURE CONTROL( HANDLING, AND ARTERIAL)

The association between dietary calcium intake, calcium metabolism, an d blood pressure form the basis of this review. Epidemiologic data con sistently show an inverse relationship between dietary calcium and blo od pressure. Clinical trials of calcium supplementation have not been as consistent in outcome. Approximately two-thirds of the supplementat ion studies have found a beneficial effect of calcium on blood pressur e. The lack of consistency in outcome from the clinical trials relativ e to the epidemiological literature may be related to calcium intake. The epidemiological literature indicates an inverse relationship betwe en calcium intake and blood pressure, with those individuals with the lowest calcium intake (<700 mg/day) having the highest blood pressure. Clinical studies utilizing patients with high baseline calcium levels (>700 mg/day) may not see an effect of calcium supplementation on blo od pressure because of a ceiling effect. Supplemental calcium appears to correct a defect in calcium handling characterized by a renal calci um leak, increased circulating parathroid hormone, and increased intra cellular calcium levels. In part, the deficit in cellular calcium home ostasis may be a consequence of abnormal calmodulin activity. Specific ally, it appears that calmodulin activity is diminished in experimenta l hypertension and that increasing dietary calcium may improve calmodu lin activity in the spontaneously hypertensive rat. The deficit in cal modulin activity has the potential to interfere with a number of cellu lar processes crucial to the regulation of cell function and maintenan ce of appropriate vascular tone. It is concluded that additional resea rch should be directed toward understanding the ramifications of alter ed calmodulin activity in hypertension and the influence that dietary calcium can have on the activity of calmodulin.