Effects of exogenous fatty acids on calcium uptake by brush-border membrane vesicles from rabbit small intestine.
The uptake of a variety of fatty acids by isolated brush-border membranes from rabbit small intestine was studied. This uptake increased with acyl chain-length and was not diminished by washing of the lipid-treated membranes with 0.25 M CsBr. The binding of fatty acid was not accompanied by a decrease in endogenous acyl groups or of cholesterol and therefore corresponded to a net uptake accountable qualitatively and quantitatively by the fatty acid added to the membranes. The uptake of Ca2+ was stimulated by treatment of the membranes with low concentrations of unsaturated fatty acids (0.05 mM) as well as with various concentrations of caprylic acid (0.10-3.00 mM) and inhibited by treatment with higher concentrations of unsaturated fatty acids (0.20-0.60 mM). Saturated fatty acids had no marked effects on Ca2+ uptake. The stimulatory concentrations of unsaturated fatty acids did not change the Ca2+-binding characteristics of the membranes, whereas the higher concentrations decreased equilibrium binding of Ca2+ and very probably the number of high-affinity binding sites. The results of this study are assessed in terms of the effects of normal fatty acids found in the diet on the absorptive properties of the brush-border membranes.
Merrill
A R
AR
Proulx
P
P
Szabo
A
A
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002784:Cholesterol / Q000032:analysis; D005227:Fatty Acids / Q000494:pharmacology*; D005260:Female; D007421:Intestine, Small / Q000378:metabolism / Q000648:ultrastructure*; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D011817:Rabbits
D005227:Fatty Acids; D009829:Oleic Acids; D019301:Oleic Acid; D000001:Calcimycin; D002784:Cholesterol; D002118:Calcium