Supplemental dietary calcium attenuates the development of ventricular hypertrophy in borderline hypertensive rats /

Abstract

Hypertension affects 1 in 4 American adults (A.H.A, 1993). Hypertension is one risk factor of heart disease, along with heredity, gender and age. Researchers have developed the Spontaneously Hypertensive Rat (SHR) genetically hypertensive model, but investigative quandaries are limited due to secondary pressure-related changes. The Borderline Hypertensive Rat (BHR) succeeded the SHR in 1980 (F1 generation of SHR x WKY) and is an early predictor of future established hypertension. Arterial hypertension is studied at its inception in the BHR along with associated myocardial alterations. Hypertensive SHR experience left ventricular hypertrophy as an adaptive reaction to increased pressure overloadlafterload. Studies have linked restricted dietary calcium intake to hypertension and hypertrophy in subpopulations with defective calcium metabolisms (low extracellular calcium) such as the SHR. The condition is reversed by high calcium, ameliorating hypertension and hypertrophy in certain human and animal subpopulations. This study tested the hypothesis that increased dietary calcium suppresses or reduces the development of hypertension and hypertrophy in the BHR. Tail-cuff plethysmography and scanning electron microscopy were used to evaluate systolic blood pressure (SBP) and ultrastructural myocardial morphology respectively. Results of this study demonstrated that dietary calcium may have influenced SBP in the BHR. Cardiac morphology suggested that calcium also influenced the BHR heart architecture. Heart weightlbody weight ratio and hypertrophy index in BHR and BHR calcium hearts were greater than WKY, indicating hypertrophy. Left ventricular wall and interventricular wall thickness were greater in BHR than BHR CaCh or WKY. This data suggests that while dietary calcium did not consistently influence SBP, it did modulate the development of hypertrophy in the BHR.