Recent developments in intestinal calcium absorption.
Calcium absorption proceeds by transcellular and paracellular flux, with the latter accounting for most absorbed calcium when calcium intake is adequate. Vitamin D helps regulate transcellular calcium transport by increasing calcium uptake via a luminal calcium channel and by inducing the cytosolic calcium transporting protein, calbindinD(9k). Recent studies utilizing knockout mice have challenged the functional importance of the channel and calbindin. To integrate the new findings with many previous studies, the function of the two molecules must be evaluated in the calcium transport and economy of mice. When calcium intake is high, transcellular calcium transport contributes little to total calcium absorption. Therefore, increasing calcium intake seems the most effective nutritional approach to ensure adequate absorption and prevent bone loss.
Bronner
Felix
F
The University of Connecticut Health Center, Farmington, Connecticut 06030-6125, USA. bronner@neuron.uchc.edu
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D064026:Calbindins; D002118:Calcium / Q000493:pharmacokinetics*; D015220:Calcium Channels / Q000172:deficiency / Q000502:physiology; D004058:Diffusion; D004386:Duodenum / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D007421:Intestine, Small / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D064030:S100 Calcium Binding Protein G / Q000235:genetics / Q000502:physiology; D050916:TRPV Cation Channels / Q000172:deficiency / Q000502:physiology; D014807:Vitamin D / Q000031:analogs & derivatives / Q000502:physiology
D064026:Calbindins; D015220:Calcium Channels; D064030:S100 Calcium Binding Protein G; D050916:TRPV Cation Channels; C446923:Trpv6 protein, mouse; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D002118:Calcium