CHANGES BY PROGESTERONE DERIVATIVES IN FATTY-ACIDS FROM PHOSPHATIDYLCHOLINE AND PHOSPHATIDYLETHANOLAMINE FRACTIONS IN RAT-LIVER ENDOPLASMIC-RETICULUM

The effects of two progesterone metabolites on fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from tot al liver and liver microsomes were studied in female rats. 16 alpha-Hy droxyprogesterone significantly increased the amount of fatty acids es terified to PC and PE fractions in total liver and liver microsomes. B oth saturated and unsaturated fatty acyl components were enhanced. In contrast, 5 beta-pregnan-3 alpha-ol-20-one caused a reduction of fatty acids bound to PC and PE fractions from total liver and liver microso mes. Pregnanolone decreased both saturated and unsaturated fatty acids . Changes in specific fatty acids occurred in palmitic and stearic aci ds among saturated components, and palmitoleic, oleic, linoleic, eicos atrienoic, arachidonic and docosahexenoic acids among unsaturated ones . The unsaturated: saturated fatty acid ratio was raised by 16-alpha-h ydroxyprogesterone and lowered by 5 beta-pregnan-3 alpha-ol-20-one in all phospholipid fractions. The induction of drug metabolizing enzymes by 16 alpha-hydroxyprogesterone may be related to an enhanced synthes is of microsomal phospholipids containing unsaturated fatty acids, par ticularly arachidonic and docosahexenoic acids. In contrast, the inhib ition of drug metabolism by 5 beta-pregnan-3 alpha-ol-20-one is associ ated with reduced formation of unsaturated fatty acyl side chains.