TY - JOUR
T1 - Effects of high calcium intake on blood pressure and calcium metabolism in young SHR
AU - Stern, Naftali
AU - Lee, David B.N.
AU - Silis, Vincent
AU - Beck, Frances W.J.
AU - Deftos, Leonard
AU - Manolagas, Stavros C.
AU - Sowers, James R.
PY - 1984
Y1 - 1984
N2 - Increased dietary calcium intake in the adult spontaneously hypertensive rat (SHR) has been reported to correct low serum ionized calcium concentration ([Ca++]) and to result in a significant amelioration of the prevailing hypertension. In the present study we examined several parameters of calcium metabolism in young (6-week-old) SHR and compared them with those observed in normotensive Wistar-Kyoto (WKY) rats fed equal amounts of a diet containing normal quantities of calcium (0.4%, wt/wt) for 4 weeks. A separate group of SHR was placed on an equal amount of a high calcium (2.8%, wt/wt) but otherwise identical diet. In SHR and WKY eating a normal calcium diet, serum total calcium concentration was not different, but [Ca+ +] was lower in SHR (1.58 ± 0.06 vs 1.91 ± 0.07 mmol/liter, p < 0.01). Serum immunoreactive parathyroid hormone (PTH) was increased in some, but not all, SHR. No difference was noted between the two groups in the following parameters: calcium intake, serum 1,25 dihydroxycholecalciferol (1,25(OH)2D3), urinary calcium excretion, fractional stool calcium content ([stool calcium/calcium intake] x 100), and in vitro 4SCa uptake by everted gut sacs constructed from segments of duodenum, mid-jejunum, ileum, and proximal colon. A high calcium diet corrected the abnormal serum [Ca+ +] and PTH but did not alter the progression or severity of the hypertension in SHR. A lower net weight gain was observed in SHR on a high calcium diet when compared to SHR eating normal calcium diet (9.1 ± 1.8 vs 27.0 ± 2.0 g). This was attributed, at least in part, to a consistently higher urinary sodium loss in the former group of rats (p < 0.05-0.001 throughout the study period). The progression of hypertension, even in the face of normalized serum [Ca+ + ] in young SHR, suggests that low [Ca+ + ] and hypertension do not have a cause-and-effect relationship. Sustained natriuresis caused by the augmented dietary calcium intake and increased urinary calcium excretion may contribute to the blood-pressure-lowering effect reported in adult SHR.
AB - Increased dietary calcium intake in the adult spontaneously hypertensive rat (SHR) has been reported to correct low serum ionized calcium concentration ([Ca++]) and to result in a significant amelioration of the prevailing hypertension. In the present study we examined several parameters of calcium metabolism in young (6-week-old) SHR and compared them with those observed in normotensive Wistar-Kyoto (WKY) rats fed equal amounts of a diet containing normal quantities of calcium (0.4%, wt/wt) for 4 weeks. A separate group of SHR was placed on an equal amount of a high calcium (2.8%, wt/wt) but otherwise identical diet. In SHR and WKY eating a normal calcium diet, serum total calcium concentration was not different, but [Ca+ +] was lower in SHR (1.58 ± 0.06 vs 1.91 ± 0.07 mmol/liter, p < 0.01). Serum immunoreactive parathyroid hormone (PTH) was increased in some, but not all, SHR. No difference was noted between the two groups in the following parameters: calcium intake, serum 1,25 dihydroxycholecalciferol (1,25(OH)2D3), urinary calcium excretion, fractional stool calcium content ([stool calcium/calcium intake] x 100), and in vitro 4SCa uptake by everted gut sacs constructed from segments of duodenum, mid-jejunum, ileum, and proximal colon. A high calcium diet corrected the abnormal serum [Ca+ +] and PTH but did not alter the progression or severity of the hypertension in SHR. A lower net weight gain was observed in SHR on a high calcium diet when compared to SHR eating normal calcium diet (9.1 ± 1.8 vs 27.0 ± 2.0 g). This was attributed, at least in part, to a consistently higher urinary sodium loss in the former group of rats (p < 0.05-0.001 throughout the study period). The progression of hypertension, even in the face of normalized serum [Ca+ + ] in young SHR, suggests that low [Ca+ + ] and hypertension do not have a cause-and-effect relationship. Sustained natriuresis caused by the augmented dietary calcium intake and increased urinary calcium excretion may contribute to the blood-pressure-lowering effect reported in adult SHR.
KW - 1
KW - 25(OH)2D
KW - Calcium
KW - Sodium
KW - Spontaneously hypertensive rat
UR - http://www.scopus.com/inward/record.url?scp=0021678892&partnerID=8YFLogxK
U2 - 10.1161/01.HYP.6.5.639
DO - 10.1161/01.HYP.6.5.639
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AN - SCOPUS:0021678892
SN - 0194-911X
VL - 6
SP - 639
EP - 646
JO - Hypertension
JF - Hypertension
IS - 5
ER -