Release characteristics of a free polyunsaturated fatty acid from an oily lymphographic agent

The release profiles of a free polyunsaturated fatty acid, alpha-linolenic acid, from solutions in an oily lymphographic agent Lipiodol-Ultra-Fluid (Lipiodol), to rabbit and human plasma, phosphate buffer solution (PBS), and PBS containing bovine serum albumin (BSA) were examined in vitro. The times required for 50% release of alpha-linolenic acid from Lipiodol were about 1 and 1.5 h in the rabbit and human plasma, respectively. Although only a slight amount of alpha-linolenic acid was released from Lipiodol to PBS after 24 h incubation at 37 degrees C, release was markedly enhanced by the addition of BSA to PBS. The amount of alpha-linolenic acid released from Lipiodol into PBS containing 5% BSA increased as the alpha-linolenic acid content in Lipiodol was increased. In all experiments, the release had stopped before all alpha-linolenic acid had been released. The prolongation of alpha-linolenic acid release from Lipiodol is considered a requisite for a selective anticancer effect of Lipiodol containing a free fatty acid on liver cancer.