Influence of contraceptive steroids on the turnover of plasma free arachidonic and oleic acids.

The turnover of plasma free oleic and arachidonic acids was determined in five healthy women before and after 3 months contraceptive treatment with a daily dose of 0.05 mg ethinyl estradiol and 0.25 mg d-norgestrel administered in a cyclic manner. The contraceptive steroids did not significantly influence the total plasma free fatty acid (FFA) concentration or the turnover of oleic acid. However, during hormone administration the fractional turnover of arachidonic acid increased by 40 per cent and its arterial concentration fell by 20 per cent. The portion of saturated fatty acids in the FFA fraction decreased during the contraceptive treatment. It is concluded that the treatment with contraceptive steroids (1) had no effect on the turnover of the main part of the FFA fraction, (2) increased the transport of the polyunsaturated arachidonic acid through the plasma pool, possibly as an effect of the estrogen component, and (3) stimulated the desaturation of saturated fatty acids to monoenes.