The effects of dietary calcium on blood pressure in spontaneously hypertensive rats may be mediated by parathyroid hypertensive factor.
A high calcium intake has been shown to attenuate the degree of hypertension in spontaneously hypertensive rats (SHR) and some human hypertensives. Conversely, a low calcium intake has been associated with an increase in blood pressure in both groups. In the present study, the effects of a high (2%), medium (0.6%) and low (0.02%) calcium diet on mean arterial pressure (MAP) and on the expression of a novel circulating hypertensive factor--parathyroid hypertensive factor (PHF)--were examined in SHR. In rats on the low calcium diet, MAP and PHF activity were significantly higher at 8 weeks than in the other two groups. In the high calcium group, MAP was significantly lower than in the other two groups, although it was elevated compared to week 0 values. PHF activity was not detected in the plasma of this high calcium group. Overall, MAP was highly correlated with PHF activity (r = 0.78, P = .0001). These results suggest that the effects of dietary calcium on blood pressure in SHR may be mediated by a novel circulating hypertensive factor, PHF, such that a high calcium diet inhibits, and a low calcium diet stimulates, the expression of this factor.
Lewanczuk
R Z
RZ
Department of Physiology, University of Alberta, Edmonton, Canada.
Chen
A
A
Pang
P K
PK
D000818:Animals; D001685:Biological Factors / Q000097:blood / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects*; D002136:Calcium, Dietary / Q000494:pharmacology*; D015999:Multivariate Analysis; D010281:Parathyroid Hormone / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR
D001685:Biological Factors; D002136:Calcium, Dietary; D010281:Parathyroid Hormone; C064505:parathyroid hypertensive factor