High Fat Diet and Oxidant-Antioxidant Status of Blood 23 Fig. 3. The effect of the low-fat (LF), and high-fat (HF) diets containing lard, sunflower oil, or fish oil on (A) plasma ability to reduce Fe (III) in tripyridyltriazine complex (FRAP test), and (B) plasma capacity to scavenging 1,1- diphenyl-2-picrylhydrazyl radicals (DPPH test). Values are expressed as mean ± SEM (n = 5–10). A significant differences are as follows: a p<0.05 vs other LF or HF diets; b p<0.01 vs other LF diets; c p<0.05 vs the corre- sponding LF diet. addition, deproteinized antioxidant plasma activity in the DPPH test was significantly lower in rats fed low-FO than in animals fed low-lard and low-SO (p<0.05; Fig. 3B). Only a tendency to increase plasma anti-DPPH activity between rats fed high-SO and those fed the other high-fat diets was noted. Discussion Luminol-dependent CL is a sensitive tool for phagocyte oxidative burst determination [25]. In our study, the baseline and PMA-stimulated reactive species production by blood phagocytes, mainly due to the oxidant-generating enzyme NADPH oxidase, a leakage of ROS from the mitochondrial chain [19, 26], and to some extent by the xanthine-xanthine oxidase system [27] were significantly different between Vol. 47, No. 1, 2010 high-fat and low-fat fed rats depending on the fat source in the diet. The different effect of FO diet rich in n-3 PUFA and SO diet rich in n-6 PUFA on reactive species production by blood neutrophils in the present in vivo study is in accordance with the findings of in vitro studies. It has been found that n-3 PUFA suppressed the stimulated production of superoxide radicals by human neutrophils [28], and inhibited the NADPH oxidase-dependent superoxide radical production in the whole and disrupted neutrophils com- paring to the effect of arachidonic acid [29]. Moreover, two- week pretreatment of rats with eicosapentaenoic fatty acid (C20:5n-3) resulted in attenuation of the pulmonary macro- phage respiratory burst [30]. In contrast, n-6 PUFAs are able to directly promote NADPH oxidase assembly and activation [31, 32]. The main component of sunflower oil, linoleic acid (C18:2n-6), may also indirectly activate NADPH oxidise by protein kinase C stimulation [33, 34]. Serezani et al. [35] have demonstrated that linoleic acid stimulates neutrophil H2O2 release in a dose-dependent and NADPH oxidase-dependent manner. Further, they reported that linoleic acid-induced H2O2 generation depends on 5- lipooxigenase activity and leukotriene B4 synthesis. An augmentation of leukotriene B4 in rat leukocytes in response to the addition of sunflower oil to a basic fish oil diet has been reported also in the earlier study [36]. Our results confirmed in vivo that a high-SO diet causes greater blood phagocyte oxidative burst than an ingestion of high FO. It may suggest that a high quantity of linoleic acid in a diet can augment the risk of tissues microinjury by circulating neutrophils [37]. The mechanism of the oxidant-generated enzyme inhibi- tion by saturated fatty acids is less easily recognized and understood. To our knowledge there are no studies which demonstrate a direct effect of saturated fatty acids on NADPH oxidase activity. However, it has been found that coconut oil-enriched diet in rats significantly reduced the generation of O2- in neutrophils, partially due to the reduc- tion of glucose-6-phosphate dehydrogenase activity [38]. Furthermore, the carnitine palmitoyltransferase and cyto- chrome oxidase activities were found to be lower in brown adipose tissue of rats fed lard than of those fed high-PUFA [39]. It is also likely, that ingestion of high saturated fat decreased the saturated fatty acid to PUFA ratio in neutro- phil membranes resulted in a decrease in oxidative species- generated enzyme activity in blood phagocytes. The current determination of the erythrocyte GSH/GSSG ratio and total antioxidant capacity of plasma showed that an augmented phagocyte oxidative burst in high-SO fed rats did not cause parallel pro-oxidative changes in RBC and blood plasma. The lowest GSH/GSSG ratio showing up the intracellular thiol redox potential [17] was found in both low-SO and high-SO fed rats. However, plasma capability to reduce ferric ions was greater in these rats compared to