Relation of Certain Bile Acids to Absorption of β-Carotene in the Rat. ∗

Abstract

In previous work from this laboratory 1 it has been shown that deoxycholic acid acts as a carrier of irradiated ergosterol and of β-carotene across the intestinal tract of the rat. This is probably due to the formation of the respective choleic acids. 2 The present experiments were undertaken to determine whether or not taurocholic acid, glycocholic acid, and decholin can transport β-carotene in a manner similar to that of deoxycholic acid.

Two series of procedures were employed. In the first series vitamin A deficient bile fistula rats were fed a mixture of β-carotene and the bile acid under test. The vaginal smear picture was used as an index of absorption and utilization of β-carotene. Each animal received 100 γy of β-carotene daily during the test period. The activity of the carotene was controlled by feeding similar doses of the β-carotene-bile acid mixtures to unoperated vitamin A deficient rats. Thirteen bile fistula rats were employed for the glycocholic acid group, 12 for the taurocholic acid group, and 11 for the decholin group. With the exception of one rat in the glycocholic acid group none of the bile fistula rats responded to the administration of β-carotene. The vaginal smear pictures of the unoperated vitamin A deficient rats returned to normal. Under similar experimental conditions absorption of β-carotene takes place when deoxycholic acid is fed to bile fistula rats.

In the second series attempts were made to prepare compounds of β-carotene with each of the three bile acids under consideration. Ten milligram portions of β-carotene were mixed with 6 molecular equivalents of the bile acid. The mixtures were sealed in glass tubes under nitrogen and heated in a paraffin bath to 185-190† for 5 minutes. The melt was dissolved in an excess of 5% sodium carbonate solution. The filtered solutions were extracted with peroxide-free ether. Some of the solutions were previously acidified, others were not. The first part of the extract was discarded in order to remove any uncombined carotene. The remaining portions of the extracted material were evaporated to dryness in an atmosphere of nitrogen. The residue was dissolved in sodium carbonate solution and the process of extraction, evaporation, and solution was repeated. A similar experiment was carried out with deoxycholic acid.