Endocrine Abstracts (2003) 6 P61

Prostaglandin production and timing of parturition in sheep fed a diet high in n-6 polyunsaturated fatty acids

M Elmes1, K Poore2, J Newman2, LR Green2, Z Cheng1, DRE Abayasekara1, MA Hanson2 & DC Wathes1

1Reproduction and Development, Royal Veterinary College, Herts, AL9 7TA, UK; 2Centre for Fetal Origins of Adult Diseases, University of Southampton, SO16 5YA, UK.

Recent health reports state that the population of western countries is consuming excessive amounts of n-6 polyunsaturated fatty acids (PUFAs) in the diet. Dietary n-6 PUFAs are precursors for prostaglandin (PG) synthesis, which play important roles in parturition. Increased dietary n-6 PUFA could thus alter PG production. This study determined the effect of a high n-6 PUFA diet on PG production and the timing of the onset of labour. Pregnant Welsh Mountain ewes were fed an isoenergetic control (n=5) or SoyPreme (a protected form of soya, high in the n-6 PUFA linoleic acid, n=6) diet from 100 days gestation (normal term is 145dGA). At 131dGA, ewes and fetuses were surgically instrumented under general anaesthesia (750mg sodium thiopentone i.v. and 2% halothane in O2 with vascular catheters and myometrial electrodes. Myometrial electromyographic (EMG) activity was monitored continuously after surgery and after 7 days postoperative recovery blood was sampled for analysis of maternal PGFM, progesterone (P4) and oestradiol (E2) and fetal PGFM and PGE2. Data are expressed as mean ± SEM. Labour induction was initiated on 139dGA using continuous infusion of dexamethasone (DEX, 1mg/day, I.V.) to the fetus. Ewes on the n-6 PUFA diet entered established labour earlier after DEX induction compared to control ewes (twice basal EMG activity reached at 35 ± 2.8 h vs. 42 ± 1.1h, P < 0.05). Maternal and fetal plasma concentrations of PGFM and PGE2 were doubled by the high n-6 diet from d138 until delivery on d141, P<0.05). Maternal concentrations of P4 and E2 were similar in control and high n-6 PUFA groups prior to DEX. After DEX induction, plasma E2 in high n-6 PUFA ewes increased earlier than control ewes to levels significantly above basal. The ability of a high n-6 PUFA diet to cause such an increase in plasma PG levels and earlier onset of labour suggests that diet could be a contributing factor to premature birth. Supported by BBSRC

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