RESUMEN
Long chain n-6 and n-3 fatty acids play important roles in labor and delivery. These effects may be mediated by prostaglandin (PG) synthesis and by regulation of matrix metalloproteinases (MMPs), both of which play roles in uterine contraction, cervical ripening and rupture of fetal membranes. The effects of altering dietary n-6:n-3 long chain fatty acid ratios, and the addition of dietary conjugated linoleic acids (CLA) and docosahexaenoic acid (DHA) on fatty acid composition of reproductive tissues, PG synthesis in liver and reproductive tissue and serum MMP levels were examined in pregnant rats. Modified AIN-96G diets with n-6:n-3 ratios of 7:1 and 34:1 with and without added 1.1% (by weight) conjugated linoleic acid (CLA) and/or 0.3% (by weight) DHA were fed through day 20 of gestation. Reproductive tissues readily incorporated both DHA and CLA. CLA significantly (P<0.05) depressed PGF(2 alpha)synthesis in placenta, uterus and liver by 50% when the n-6:n-3 ratio was 7:1 and by 66% at 34:1 ratio. Significant differences (P<0.05) in PGE(2)synthesis in uterus and liver were seen only between groups fed the high ratio of n-6:n-3 without CLA, and the low ratio with CLA. Addition of CLA to DHA containing diets depressed PGF(2alpha) by one-third in uterus and liver (P<0.05). Serum MMP-9 and active MMP-2 were suppressed (P<0.05) by addition of either CLA or DHA.