The effect of dietary calcium content and oral vitamin D3 supplementation on mineral homeostasis in a subterranean mole-rat Cryptomys damarensis

The Damara mole-rat, Cryptomys damarensis, has no access to obvious dietary or endogenous sources of vitamin D. We tested the hypotheses that mineral metabolism in these animals is independent of vitamin D status but rather is affected by dietary calcium (Ca) content. Furthermore, we questioned whether bone and teeth assist in plasma mineral homeostasis. Mole-rats increased Ca intake when dietary Ca content increased; however, mode of gastrointestinal uptake, vitamin D metabolite and plasma Ca concentrations were not altered. Similarly, oral vitamin D supplementation did not affect gastrointestinal Ca absorption or alter plasma Ca concentration, although significant increases in plasma concentrations of vitamin D were evident. Bone and teeth mineral (Ca and P_i) content were augmented with vitamin D supplementation. Mineral homeostasis was primarily maintained by manipulating mineral deposition in teeth, for mineral content in teeth increased significantly when dietary Ca content changed from 1.3 g/kg to 2.6 g/kg and higher. Mineral homeostasis in these subterranean rodents does not appear to be regulated at the level of the intestine, but rather by manipulating bone and teeth mineral reservoirs.