Modulation of rat liver lipid metabolism by prolactin

The effect of chronic hyperprolactinemia on the delta6- and delta5-desaturation activity, total lipid and fatty acid composition, as well as fluorescence anisotropy, was studied in liver microsomes from anterior pituitary-grafted rats. We observed a depression in delta6-desaturation activity but no changes in the delta5-desaturation activity in the grafted animals. The microsomal fraction from the hyperprolactinemic rats contained significantly 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 as 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 induce changes in polyunsaturated fatty acid distribution in liver microsomes, which regulates the lipid rotational mobility and hence membrane fluidity.