EFFECT OF DIETARY CALCIUM ON THE DEVELOPMENT OF HYPERTENSION AND HYPERTENSIVE VASCULAR-LESIONS IN DOCA-SALT AND 2-KIDNEY, ONE-CLIP HYPERTENSIVE RATS

Objective: To examine the effect of modest changes in dietary calcium on systolic blood pressure (SBP) and myocardial and renal vascular les ions in Sprague-Dawley rats. Design: Regular- (0.4%, by weight), high- (0.8%) or low-calcium (0.24%) diets were fed to normotensive control, deoxycorticosterone acetate (DOCA)-salt and two-kidney, one clip (2-K ,1C) hypertensive rats for 8 weeks. Methods: Tail-cuff SBP and metabol ic balance were measured once a week. At the end of the study the kidn eys and hearts were collected for histological study. Results: Dietary calcium had no effect on SBP in the DOCA-salt rats, but loading with calcium accelerated the rise in SBP in 2-K,1C rats (P<0.01, high- vers us regular-calcium diet). The high-calcium diet reduced the percentage medial area of intramyocardial arteries in the DOCA-salt and 2-K,1C h ypertensive rats. The DOCA-salt rats on the low-calcium diet had a hig her renal vascular lesion score than those on the regular- or high-cal cium diet (P<0.05). Conclusions: A high-calcium diet appears to preven t intramyocardial vascular wall thickening in DOCA-salt and 2-K,1C hyp ertensive rats, and a low-calcium diet aggravates renal vascular lesio ns in DOCA-salt hypertensive rats. These effects are not related simpl y to changes in blood pressure.