Cell membrane fluidity is modified by their lipid structure and saturated fatty acids (SFA)/unsaturated fatty acids (UFA) proportions and alterations in this coefficient (particularly, SFA/monounsaturated fatty acids (MUFA)) are related with numerous pathologies (Ntambi, 1999). However, the fatty acid incorporation pattern is different for each tissue (Soriguer et al. 2000). On the other hand, there is controversy about the influence of the quality of fat (fatty acid chain length and unsaturation index) on the pancreatic enzyme content and secretion. Studies with conscious dogs show that long-term adaptation to diets high in fat provide higher levels of lipase secretion after a sunflower-seed oil dietary intake (Yago et al. 2000).
We find that literature is scarce that relates both changes in membranes lipid composition and pancreatic adaptation, by dietary fatty acids (Begin et al. 1990).
Thirty-six male New Zealand rabbits were divided into two groups and fed for 50 days with either a standard chow (Panlab, Barcelona; control group, C, n = 6) or a atherogenic diet (95 % standard chow, 3.5 % lard and 1.5 % cholesterol, w/w; atherogenic groups, A, n = 30). Prior to analysis the animals were anaesthetized with sodium pentothal (30 mg kg -1, I.V.) and humanely killed according to international guidelines. The pancreas was removed in order to measure enzymatic activities by an enzymatic-colorimetric (amylase) and by titrimetric (lipase, colipase, trypsin and chymotrypsin) methods and fatty acid composition of plasma membrane by gas-liquid chromatography.
In the atherogenic rabbits, the intake of differents diets (98.25 % standard chow, 1.75 %: virgin olive (V), olive (O), sunflower seed (S) and fish (F) oils, w/w), during the next 30 days provide modifications in the pancreatic enzymes content, when compared with control group. The lipase activity (U (g pancreas)-1), significantly higher (P < 0.05, one-way ANOVA) in atherogenic than control group (38.54 ± 4.577, n = 6 vs. 10.14 ± 2.859, n = 6, means ± S.E.M.), continues increasing in the sunflowerseed group (87.17 ± 25.941, n = 6) when compared with the other experimental groups (25.18 ± 5.781, n = 6), 57.15 ± 12.837, n = 6, 31.40 ± 3.783, n = 6, V, O and P, respectively). These results seem to indicate a role of fat quality in lipolytic enzyme adaptation, specifically, for fats with a high content in polyunsaturated fatty acids (PUFA) (n-6). The acinar cell membrane lipid composition analysis (percentage of total fatty acids, means ± S.E.M.) indicates statistical significance in the adaptation (P < 0.05, one-way ANOVA) to dietary fatty acids profile (Table 1).
As previous studies show that the quality of fat affects different gastrointestinal peptide levels implicated in the pancreas secretion activity, the results obtained for enzymatic content and those observed for membrane lipid composition suggest that the type of fat preferentially affects the enzymatic secretion (Hedemann et al. 2001). This fact may to be relevant in the investigation and treatment of pancreatic diseases such as pancreatitis or pancreatic cancer.