Upregulation of duodenal calcium absorption by poly-unsaturated fatty acids: events at the basolateral membrane

Poly-unsaturated fatty acids, especially of the n-3 series, have a benefici al effect in treatment of osteoporosis in the elderly. Duodenal calcium abs orption is a particularly vulnerable aspect of the development of this dise ase. It has been shown that the process of calcium transport through the ra t duodenal enterocyte takes place in essentially three steps: entry of calc ium through channels in the brush border (apical membrane), transcellular t ransport through the cytoplasm by calbindin and extrusion at the basolatera l membrane by Ca2+-ATPase and a Ca2+-Na+ exchanger which is driven by Na+, K+-ATPase. This paper presents a hypothesis that poly-unsaturated fatty aci ds can modulate both Ca2+-ATPase and Na+, K+-ATPase activity either by a di rect action on the enzyme or by phosphorylation processes via protein kinas es A and C and thus exert their positive influence on calcium absorption in this manner. (C) 2001 Harcourt Publishers Ltd.