Abstract
Abstract. Norethisterone acetate (NET) was administered to 11 oophorectomized women (mean age 34.5 ± 5.9 years) primed with the 17-C-alkylated ethinyl oestradiol (EOe) and the non-alkylated oestrogen, oestradiol valerate (Oe2V) in separate periods. Blood samples were drawn after 4 weeks without hormonal replacement therapy, after 6 weeks on each oestrogen and after 6 weeks on each oestrogen-progestogen combination. Routine liver function tests were carried out, assessment of individual phosholipids i.e. cephalin, lecithin, lysolecithin and sphingomyelin was done after thin layer chromatography. The relative fatty acid composition of serum and high density lipoprotein lecithin and serum cholesterol ester was determined by gas liquid chromatography. The redistribution of serum individual phospholipids (increase in lecithin and decrease in lysolecithin) induced by both oestrogens was reversed by the addition of NET. This lecithin-lysolecithin shift seen after NET administration could depend on a stimulation of the hepatic lipase with its phospholipase Al-activity. The 17-C-alkylated EOe, but not the non-alkylated Oe2V, caused an increase in palmitic and a decrease in stearic acid in the 1-position of serum lecithin. When NET (like EOe, 17-C-alkylated) was added to EOe, this palmitic-stearic acid shift was further accentuated, and it also appeared when NET was added to Oe2V. It is suggested that the shift in 1-position fatty acids of serum lecithin induced by EOe and NET is a non-hormonal 'drug-effect' linked to their 17-C-alkylation and liver toxicity. The reduction in arachidonic acid of serum lecithin and serum cholesterol ester seen after NET administration is interpreted as an anti-oestrogenic effect which could be mediated by a decreased transformation of linoleic to arachidonic acid in the liver.
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