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 beneficial effect in treatment of osteoporosis in the elderly. Duodenal calcium absorption is a particularly vulnerable aspect of the development of this disease. It has been shown that the process of calcium transport through the rat duodenal enterocyte takes place in essentially three steps: entry of calcium through channels in the brush border (apical membrane), transcellular transport through the cytoplasm by calbindin and extrusion at the basolateral membrane by Ca(2+)-ATPase and a Ca(2+)-Na(+)exchanger which is driven by Na(+), K(+)-ATPase. This paper presents a hypothesis that poly-unsaturated fatty acids can modulate both Ca(2+)-ATPase and Na(+), K(+)-ATPase activity either by a direct action on the enzyme or by phosphorylation processes via protein kinases A and C and thus exert their positive influence on calcium absorption in this manner.
Haag
M
M
Department of Physiology, University of Pretoria, PO Box 2034, Pretoria, 0001, South Africa. mhaag@medic.up.ac.za
Kruger
M C
MC
D000818:Animals; D001485:Basement Membrane / Q000201:enzymology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004386:Duodenum / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D007408:Intestinal Absorption / Q000187:drug effects*; D010766:Phosphorylation; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D015854:Up-Regulation
D005231:Fatty Acids, Unsaturated; D019831:Sodium-Calcium Exchanger; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium