The effect of dietary supplementation with linoleic and gammalinolenic acids on the pressor response to angiotensin II--a possible role in pregnancy-induced hypertension?

Dietary supplementation with 3 g/day linoleic acid, 32 mg/day gammalinolenic acid and co-factors for prostaglandin synthesis was given to 10 pregnant and 10 non-pregnant subjects for a week. Their pressor response to the infusion of three doses of angiotensin II (AII) (pregnant: 4, 8, 16 ng kg-1 min-1: non-pregnant: 1, 2, 4 ng kg-1 min-1) was then compared with that of 40 pregnant and 24 non-pregnant controls who had not been given such supplementation. Dietary supplementation was not associated with changes in basal systolic or diastolic blood pressure or heart rate during the week of treatment in pregnant or non-pregnant subjects. Basal systolic blood pressure, diastolic blood pressure and heart rate values did not differ between the treated and untreated subjects in each group. The diastolic pressor response to AII was significantly less after treatment at all doses; the effect was more marked in the pregnant subjects. The systolic response to AII, normally less than the diastolic, was somewhat blunted in the treated pregnant patients at the two higher infusion doses. No significant effect was found in the non-pregnant group. Evidence from other studies suggests that increasing plasma linoleic acid concentrations leads to increased plasma concentrations of epoprostenol (prostacyclin, PGI2) while increased availability of gammalinolenic acid is associated with a rise in prostaglandin E1 and E2 production. Pregnancy-induced hypertension is associated with a diminished tissue production of both epoprostenol and E series prostaglandins, and with an enhanced pressor response to AII.(ABSTRACT TRUNCATED AT 250 WORDS)