Maternal Essential Fatty Acid Supplementation Increases Zinc Absorption in Neonatal Rats: Relevance to the Defect in Zinc Absorption in Acrodermatitis Enteropathica

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Abstract
Summary: Pregnant zinc deficient and zinc adequate rats were injected subcutaneously with evening primrose oil throughout gestation and for 3 days post partum. The nursing pups were injected intragastrically with zinc-65 on day 3 of life and sacrificed 4 h later. The % of the total injected zinc recovered in the carcass (minus the gut and gut contents) was significantly increased in those pups nursed by mothers injected with evening primrose oil, regardless of their dietary zinc intake. The fatty acid composition of the total lipid extract of the gut and gut contents of the neonates with increased zinc-65 absorption indicated that these pups had higher proportions of arachidonic acid and other metabolites of linoleic acid than did those with lower zinc-65 absorption. In other 3-day-old rat pups, intragastric injection of linoleic, gamma-linolenic or dihomo-gamma-linolenic acids along with the dose of zinc-65 very significantly increased zinc-65 absorption in a dose-related manner. Arachidonic acid however had no significant effect on zinc-65 absorption. Prostaglandin E1 caused a significant increase in zinc-65 absorption but prostaglandin E2 had no consistent effect. Indomethacin caused a dose-related inhibition of zinc-65 absorption. Speculation: The increase in absorption of zinc-65 in neonatal rats suckled by mothers previously treated with evening primrose oil (81% essential fatty acids) is probably due to the transfer, in the breast milk, of increased amounts of the essential fatty acids-linoleic, gamma-linolenic, and dihomo-gamma-linolenic acid-and possibly prostaglandin El. It is suggested that this observation can account in part for the fact that human breast milk increases the absorption of zinc by human infants when compared with cow's milk formulae. The data would furthermore indicate that the onset of the symptoms of acrodermatitis enteropathica, which invariably occurs on weaning from human breast milk, may be exacerbated by the significantly lower essential fatty acid content of cow's milk or milk formulae compared to human breast milk. Essential fatty acids and possibly some of their metabolites such as prostaglandin El, which are present in human breast milk, may therefore be important for adequate zinc absorption in the neonatal period.

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