Factors affecting the absorption of vitamin K-1 in vitro.

Factors which might affect the absorption of vitamin K of dietary origin were investigated using everted small bowel sacs. Increasing the bile salt concentration to 20 mM or the addition of long chain fatty acids, monoolein, or lecithin all resulted in significant (P less than 0-05) decrease in the absorption rate of the vitamin. The addition of 2-5 mM short and medium chain fatty acids did not change the absorption rate of vitamin K-1 (P greater than 0-05). The absorption rate of vitamin K-1 appears to be modified by the presence of compounds in the incubation medium which either alter the partition of the vitamin between the micelle and the cell membrane or which change the permeation characteristics of the compound through the unstirred water layer or modify the physical characteristics of the cell membrane itself. It is possible that some of the above factors modify the absorption of lipid soluble compounds in general.