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  • 1
    Electronic Resource
    Electronic Resource
    Three levels of dietary calcium-effects on blood pressure and electrolyte balance in spontaneously hypertensive rats (1992)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 346 (1992), S. 542-549 
    Details
    ISSN: 1432-1912
    Keywords: Blood pressure ; High calcium intake ; Intracellular free calcium ; Na+ :K+ ratio ; Spontaneously hypertensive rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of three levels of calcium intake on blood pressure (BP) and electrolyte balance were studied for 12 weeks in spontaneously hypertensive rats (SHR): the chow of the SHR-1 group contained 1.1% calcium, and that of the supplemented groups 2.1% (SHR-2) and 3.1% (SHR-3) calcium. Wistar-Kyoto rats on a 1.1% calcium diet (WKY-1) served as normotensive controls. After 10 and 12 weeks BP was significantly lower in both calcium-supplemented groups than in the SHR-1 group, the SHR-2 and SHR-3 groups not deviating from each other. Platelets and lymphocytes were used as experimental cell models to study the effects of the calcium diets on intracellular free calcium ([Ca2+]i) level, which was measured by the fluorescent indicator quin-2. At the end of the study [Ca2+]i was lower in both cell types in SHR-2 and SHR-3 than in SHR-1, the supplemented groups being comparable to each other. In platelets [Ca2+]i still remained higher in the calcium-treated than the WKY-1 group, while in lymphocytes the levels were similar between SHR-2, SHR-3 and WKY-1. Plasma sodium, calcium and magnesium levels did not differ in the SHR groups, but plasma potassium was higher in both supplemented groups than in SHR-1. Plasma renin activity was comparable in SHR-1, SHR-2 and WKY-1, but was suppressed in the SHR-3 group. Creatinine clearance in the SHR-3 group was higher than in SHR-1 and SHR-2, but still remained lower than in WKY 1. High calcium intake was associated with a dose-dependent increase in urinary magnesium excretion, while the excretions of sodium and potassium were proportional to the intakes. The tissue Na+ :K+ ratio in abdominal aorta and tail artery was reduced in SHR-2,.but only a nonsignificant tendency was observed in SHR-3 when compared with the SHR-1 group. In summary, high calcium intake reduces [Ca2+]i in both platelets and lymphocytes in SHR, suggesting that alterations in cellular calcium regulation may explain the BP-lowering effect of calcium supplementation. Elevation of dietary calcium level from 1.1% to 2.1% is associated with a lowering of the Na+ :K+ ratio in the arterial wall. A further increase in calcium content from 2.1% to 3.1% appears to have a favourable effect on renal function in SHR, but also aggravates magnesium loss into the urine. During the higher supplemented calcium intake, suppression of the renin-angiotensin system seems to be involved in the lowering of BP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169011
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of high calcium intake on Ca2+ ATPase and the tissue Na:K ratio in spontaneously hypertensive rats (1992)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 345 (1992), S. 117-122 
    Details
    ISSN: 1432-1912
    Keywords: Blood pressure ; Ca2+ATPase ; Dietary calcium loading ; Na:K ratio ; Spontaneously hypertensive rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of oral calcium loading on the development of hypertension were studied in spontaneously hypertensive rats (SHR). Forty-eight male SHR were divided into four groups according to treatment: control, calcium, deoxycorticosterone (DOC) and DOC+calcium. Both calcium groups received ad libitum 1.5% CaCl2 as drinking fluid. The DOC animals were injected with a mineralocorticoid, deoxycorticosterone trimethylacetate, 25 mg/kg, s. c., once a week. Systolic blood pressure (BP) was measured once a week by the tail cuff method. During the nine-week study, the development of hypertension was enhanced in the DOC group, while in the calcium group a blood pressure-lowering effect was observed when compared to the controls. Calcium also abolished the hypertensive effect of DOC. The maximal velocity of calcium transport was higher in “insideout”-vesicles of red blood cells as compared to controls in both calcium-supplemented groups. DOC treatment resulted in elevated sodium and potassium contents in tail artery tissue, while the effect of the combination of DOC+calcium was equal to controls. On the other hand, the tissue Na:K ratio was decreased in both tail artery wall and heart in the calcium group. Calcium treatment diminished the excretion of phosphate in both groups, while the plasma phosphate concentration was lowered in the calcium group. In mesenteric arterial rings, DOC impaired nitro-prusside-induced relaxation, while the relaxation was enhanced compared to control in both the calcium and DOC+calcium groups. As a summary, it can be assumed that in the calcium group, a higher rate of calcium extrusion via Ca2+ ATPase together with a reduction in the tissue Na:K ratio, possibly reflecting a change in Na+K+ ATPase activity, partially explain the beneficial effects of high calcium intake in blood pressure. The combination DOC+calcium, in turn, seems to oppose the effects of DOC on blood pressure via higher rate of calcium extrusion and by returning the tissue sodium and potassium contents to the control level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175478
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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