Calcium metabolism and bone mass in female rabbits during skeletal maturation: Effects of dietary calcium intake

This study documents growth and dual-energy X-ray absorptiometry (DXA)-dete rmined peak bone mass profiles in the rabbit model, and tests the hypothesi s that rabbits show patterns of bone accretion similar to humans and thus m ay serve as a viable model for human bone physiology. It is also shown that dietary Ca intake affects peak bone mass and the temporal pattern of its a ttainment. Groups of weaned animals were administered two nutritionally com plete but calcium-altered diets (0.5% or 1.0% Ca). We evaluated growth, bon e mass accretion, and Ca metabolism from 20 to 56 weeks of age in both the 1.0% Ca and 0.5% Ca groups of rabbits. For each monthly period, we monitore d body mass, naso-tail length, food consumption, and fecal output. In addit ion, we collected blood and 24 h urine samples for biochemical analyses, an d measured bone mass variables of the lumbar spine with DXA. The 1.0% Ca gr oup had a lower apparent fractional absorption of Ca and higher urinary Ca excretion, but retained more Ca than the 0.5% Ca group during the growth ph ase. Furthermore, the 1.0% Ca group had lower parathyroid hormone (PTH) and bone biochemical marker concentrations throughout the study than the 0.5% Ca group. The lower levels of PTH and bone markers of resorption and format ion, may have resulted in a reduction in skeletal remodeling, and this phys iological mechanism may have contributed to the 10% increase in peak bone m ineral density of the lumbar spine in the 1.0% Ca group of rabbits. (C) 200 1 by Elsevier Science Inc. All rights reserved.