Modulation of rat liver lipid metabolism by prolactin

The effect of chronic hyperprolactinemia on the Delta 6- and Delta 5-desatu ration activity, total lipid and fatty acid composition, as well as fluores cence anisotropy, was studied in liver microsomes from anterior pituitary-g rafted rats. We observed a depression in Delta 6-desaturation activity but no changes in the Delta 5-desaturation activity in the grafted animals. The microsomal fraction from the hyperprolactinemic rats contained significant ly less amount of linoleic acid and a higher content of 20:4 n-6, 22:5 n-6 and 22:6 n-3 acids. Lipid rotational mobility was increased in microsomes a s well as in liposomes obtained from the microsomes of transplanted animals . The fluidifying effect induced by PRL was located in the deepest zone of the membrane. The results obtained indicate that high levels of prolactin i nduce changes in polyunsaturated fatty acid distribution in liver microsome s, which regulates the lipid rotational mobility and hence membrane fluidit y.