Vitamin K, intestinal absorption in vivo: influence of luminal contents on transport
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چکیده
HOLLANDER, DANIEL, ELENA RIM, AND K. S. MURALIDHARA. Vitm2in K, intestind absorption in ViVO: influence of’ hninal contents on transport. Am. J. Physiol. 232(l): E69E74, 1977 or Am. J. Physiol.: Endocrinol. Metab. Gastrointest. Physiol. l(1): E69-74, 1977. -Intestinal absorption of [:3H]phylloquinone was investigated in the unanesthetized rat by the use of a technique of recirculating perfused isolated intestinal segments. Apparent saturation kinetics were found as the concentration of the vitamin in the perfusate was increased in a stepwise fashion from 15 nM to 300 PM. Alkalinization of the perfusate or the addition of 2.5 mM linoleic acid to the perfusate caused a significant (P < 0.05) decrease in the absorption rate of phylloquinone. Modifications in the perfusate concentration of sodium taurocholate, the substitution of a nonionic detergent (Pluronic F-68) for sodium taurocholate, the addition of mediumand long-chain saturated fatty acids, or the addition of vitamins K, and K:{ to the perfusate did not alter the absorption rate of the vitamin. Decreasing the thickness of the unstirred water layer by increasing the perfusion rate caused a significant increase in phylloquinone absorption rate. In vivo absorption of vitamin K, appears to be mediated by an energy requiring saturable transport mechanism. The composition of the perfusate, its PI-I, and its rate of flow are all important determinants of vitamin K, absorption rate.
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