engleski

Quantitative assessment of the effects of variability in dietary zinc dose-rate idiorrhythms upon zinc deposition in bone of weanling rats by using a slope-ratio assay

We quantitatively assessed the effect of the idiorrhythmic dose-rate variability in dietary zinc intake on zinc deposition in the femur and incissor of weanling rats by the slope-ratio analysis of analogous idiorrhyhms. In idiorrhythmic feeding the dose (x) is viewed over the period of the entire experimental epoch as a dose-time equivalent modulo (Mx) that can be divided into a series of equal products of different doses with different frequency (idiorrhythm, I). Each I is administered in a regularly recurring pattern to deliver the same dose as that from a standard daily regimen of zinc, albeit at a different rate ; Ix = [dnth Mx) / dnth, where dnth is the sequential number of zinc dosing day separated by 1 to 7 days of feeding the diet without zinc, when dnth>1. Four different Mx were tested, M3, M6, M12, and M24 providing 3, 6, 12, and 24 mg Zn kg-1 diet d-1, respectively, over a 24 day epoch ; each Mx had seven analogous Ix of different dose sites, but the same dosing frequency (dnth). The slopes for the M3, M6, and M12 analogous idiorrhythms showed that zinc deposition in the femur and incisor, as a measure of metabolic availability, varied considerably with spacing of the dose with time. Metabolic availability of zinc progressively decreased by 50% from I = Mx/1 to I = 4Mx/4. Then it rose to approach the initial I = Mx/1 values of animals fed zinc daily for I = 5Mx/5 and I = 6Mx/6, before it finally dropped again to the bottom level for I = 8Mx/8. The results showed that the impact of zinc dose-rate in dietary zinc intake is an important determinant of an adequate supply of metabolic zinc.

zinc avaialability; dose-rate idiorrhythm; calcified tissue; slope-ratio assay; weanling rat

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