The effect of calcium intake on bone composition and bone resorption in the young growing rat

Abstract

A low Ca intake by both rats and man increases bone resorption, decreases bone mass and increases the risk of osteoporosis. The skeletal effect of high Ca intakes is less clear, particularly during periods of bone mineral accrual. Twenty-four female 5-week-old rats, Wistar strain, were randomized by weight into three groups of eight rats each and fed ad libitum a semi-purified diet containing 2 (Ca-restricted), 5 (normal) or 20 (Ca-supplemented) g Ca/kg for 3 weeks. When compared with the normal Ca diet, urinary Ca excretion was unaffected by the dietary restriction of Ca for 3 weeks, but was greater (P,0 : 001) in Ca-supplemented rats. Urinary pyridinoline (Pyr) and deoxypyridinoline (Dpyr) levels were significantly greater during weeks 2 (Pyr P,0 : 05, Dpyr P,0 : 001) and 3 (Pyr P,0 : 01, Dpyr, P,0 : 001) of dietary Ca restriction, but were unaffected by Ca supplementation. Femoral dry weight and the concentration of Mg and P in femora were unaffected by dietary Ca concentration. Femoral Ca concentration was reduced (P,0 : 05) in the Ca-restricted group compared with the other two groups. In conclusion, these results suggest that increasing dietary Ca intake, well above the recommended level, had no effect on bone mineral composition or bone resorption (as assessed with urinary pyridinium crosslinks) in young growing female rats. In addition, these results confirm the findings of previous studies which have shown that bone Ca content in young growing rats was reduced by dietary Ca restriction and that this reduction results, at least in part, from an increased rate of bone resorption.

From aldosteronism to oxidative stress: the role of excessive intracellular calcium accumulation

“…37 In both rats and man, marked Na + loading alone (for example, a 8% NaCl diet) is accompanied by hypercalciuria, SHPT with bone loss and a proinflammatory vascular phenotype. [42][43][44][45][46][47][48][49][50] The likely mechanism is thought to be related to an expansion of the extravascular space, resulting in decreased proximal tubular resorption and thereby increased distal delivery of Na + , Ca 2+ and Mg 2+ , with the mineralocorticoid promoting distal tubular Na + resorption without retarding Ca 2+ or Mg 2+ excretion. [32][33][34][35][36] This may be further accentuated by nitric oxide-mediated increments in medullary blood flow.…”

“…Urinary hydroxyproline, a marker of bone resorption, is increased during ALDOST or deoxycorticosterone/salt treatment, 58 whereas the hypercalciuria seen with 8% NaCl loading alone is likewise accompanied by SHPT, with a loss of bone Ca 2+ and Mg 2+ and increased urinary excretion of various markers of bone resorption. 42,44,46 CELLULAR AND MOLECULAR PATHWAYS LEADING TO CARDIOMYOCYTE NECROSIS Pathways accounting for cardiomyocyte necrosis and subsequent scarring of myocardium found at 4 weeks ALDOST have been examined and the pathogenic role of circulating factors elucidated.…”

Protective Effect of Zinc; Against Salt Induced Macroscopic Changes in Humerus and Femur of Rats

“…21,34,35 Although, increase in the total body weight (RTBW) of all the groups during eight weeks was observed, rats in group C had highest weight gain of 54g followed by weight gain of 37g in experimental group B. Increase in weight was observed in both experimental groups but the least weight gain of 22g was observed in group A fed on high salt diet.…”

“…39 By using the following formula, relative tissue body weight index (RTBWI) 21 was calculated: RTBWI= weight of organ (g)/ body weight (g) x100.…”

“…19,20 due to change in bone mineral density and detrimental effect on calcium homeostasis. 21,22 Zinc is a component of more than 200 enzymes 14,23 and 23 most abundant element in the earth's crust with enzymatic function reduces osteoclast resorption activities and increase markers of osteoblast differentiation, matrix maturation and mineralization. 24 Zinc may increase bone formation through stimulating cell proliferation, alkaline phosphatase activity and collagen synthesis.…”