REGULAR ARTICLE Effects of dietary fish oil and corn oil on rat mammary tissue Serge Delpal & Alain Pauloin & Catherine Hue-Beauvais & Valérie Berthelot & Philippe Schmidely & Michèle Ollivier-Bousquet Received: 15 June 2012 / Accepted: 22 October 2012 / Published online: 23 November 2012 # Springer-Verlag Berlin Heidelberg 2012 Abstract The effects, on the maternal mammary gland, of diets containing similar lipid percentages but differing in composition of polyunsaturated fatty acids (PUFA) have been assessed in rats during pregnancy and lactation. For this purpose, tuna fish oil (an n-3-PUFA-enriched oil) and corn oil (an n-6-PUFA-enriched oil) were included in diets at ratios such that the caloric inputs were the same as that of the control diet. As expected, the maternal diet affected the tissue composition of dams. Unexpectedly, only the tuna fish oil diet had an effect on pup growth, being associated with the pups being underweight between the ages of 11 and 21 days. The maternal mammary gland of rats fed the tuna fish oil diet displayed two main modifications: the size of cytoplasmic lipid droplets was increased when compared with those in control rats and the mammary epithelium showed an unusual formation of multilayers of cells. These results show that the tuna fish oil diet, during pregnancy and lactation, exerts specific effects on mammary cells and on the formation of lipid droplets. They suggest that this maternal diet affects the functioning of the mam- mary tissue. Keywords Mammary tissue . Lactation . Polyunsaturated fatty acid . Lipid droplet . Rat (Wistar) Introduction The effects of dietary polyunsaturated fatty acids (PUFA) during the pre- and post-natal periods have been shown to be linked to the length of pregnancy in humans, neonatal development in humans and rats and the lifespan of older adult rats but conclusions concerning their beneficial or harmful effects differ between studies (Church et al. 2009). In brief, dietary n-3 PUFA (PUFA of the n-3 family) sup- plementation has been shown to reduce the incidence and severity of pre-term births by prolonging pregnancy and increasing infant birth weight (Olsen and Secher 1990, 2002; Olsen et al. 1992). However, some adverse effects have been described in the case of maternal dietary supple- mentation with large quantities of n-3 PUFA, resulting in reduced birth weight and greater morbidity (Olsen et al. 1992; Thorsdottir et al. 2004). Numerous studies have in- vestigated the consequences of infant formulas fortified with n-3 PUFA on neurocognitive and visual development, on body growth and on verbal skills (Scott et al. 1998; Lauritzen et al. 2005). Thus, whereas the maternal consump- tion of diets rich in PUFA during pregnancy might affect both fetal growth and the development of the mammary gland, it might, during lactation, directly affect aspects of neonatal growth and development that are entirely depen- dent on maternal milk. The secretory functioning of the mammary gland in rats is dependent on the presence of This work was supported by an institutional grant from the Institut National de la Recherche Agronomique (France) and by the Groupe Lipides et Nutrition (France). Electronic supplementary material The online version of this article (doi:10.1007/s00441-012-1523-4) contains supplementary material, which is available to authorized users. S. Delpal INRA, UR0909 Nutrition et Régulation Lipidique des Fonctions Cérébrales, 78352 Jouy-en-Josas cedex, France A. Pauloin : C. Hue-Beauvais : M. Ollivier-Bousquet (*) UR1196 Génomique et Physiologie de la Lactation, 78352 Jouy-en-Josas cedex, France e-mail: Michele.ollivier-bousquet@jouy.inra.fr V. Berthelot : P. Schmidely UMR INRA-AgroParisTech 791 Physiologie de la Nutrition et Alimentation, 16 Rue Claude Bernard, 75231 Paris cedex 05, France Cell Tissue Res (2013) 351:453–464 DOI 10.1007/s00441-012-1523-4