Effect of Calcium Intake on Calcium Absorption and Utilization in Rats

Abstract：Objective: To study the relationship between Ca2+ intake, Ca2+ absorption and Ca2+ retention.Methods; Thirty-six weaning rats were firstly fed with Ca-poor diet for a 3-week Ca2+ depletion period, and then randomly divided into 3 groups to receive diet with low, adequate and high Ca2 + contents. The experiment lasted 12 weeks,with a 3-day metabolism experiment conducted in the 5th week. Results: Supplement with adequate amount of Ca2+increased bone Ca2 + , bone mineral density (BMID), bone mineral content ( BMC ) and the weight of femur ( P ＜ 0.05 ).Higher doses of Ca2 + failed to further improve the efficiency. Analysis showed that Ca2+ intake was positively correlated to bone Ca2+ ,BND and BMC,and negatively correlated to the rates of Ca2+ absorption and retention. Dose-effect study revealed that the Ca2 + absorption rate (Y) was a hyperbola function of Ca2 + intake (X), i. e. Y = e6.8068 × X - 0.8821 + 20 ( F =47.3154,P ＜0.0001).It was found from the results that bone Ca2+ content(determined by atom absorption spectrophotometer) had a linear correlation to BMC (determined with uni-photon bone mineral densitometer). Conclusion: The rate of Ca2+ absorption is a hyperbola function of Ca2 + intake. The increment of Ca2+ absorption will be minimal when Ca2+ intake exceeds 3d 250 rng in rats. BMC,better than BMD,may substitute for the ideal bone Ca2+ content as the index to assess the efficacy of Ca2+ supplement.