Effects Of Dietary Calcium Deprivation On Urinary Calcium Excretion Rates In Laboratory Rabbits
A metabolic balance study was used to investigate the renal adaptation to dietary calcium deprivation in laboratory rabbits. This was accomplished by first feeding the rabbits a +Ca (0.9% Ca) diet to establish pre-deprivation urinary calcium excretion rates (UVq3) and urinary phosphorus excretion rates (UVp), which may be referred to as baseline values. The rabbits were then fed a calcium deficient diet (0.08% Ca) and later were re-fed the +Ca diet. Daily measurements of food and water intake as well as fecal and urinary output were made during the entire study. The urine which was collected daily was analyzed for calcium and phosphorus content, and daily urinary excretion rates of both were calculated for each rabbit. The dietary calcium deprivation diminished urinary Ca excretion within hours in the laboratory rabbit and sustained deprivation resulted in complete elimination of Ca from the urine in approximately two weeks. Re-feeding the calcium-deprived rabbits a +Ca diet resulted in the immediate appearance of Ca in the urine, but the UVq3 were persistently below pre-deprivation values. Furthermore, we have shown that pre-deprivation UVca values can be achieved and maintained or exceeded upon the re-feeding of the +Ca diet following sustained dietary calcium deprivation.