Inhibitory effect of a two day fast on reactive oxygen species (ROS) generation by leucocytes and plasma ortho-tyrosine and meta-tyrosine concentrations

Since glucose intake acutely increases reactive oxygen species (ROS) genera tion by polymorphonuclear leucocytes (PMN) and mononuclear cells (MNC), we have now investigated whether a fast over a period of 48h reduces ROS gener ation by these cells. Eight normal subjects were fasted for 48h. Blood samp les were obtained at 0, 24h and 48h. ROS generation by PMN fell significant ly at 24h (66.1 +/- 19.5 % of basal) and further at 48h (45.9 +/- 23.0 % of basal; p<0.001). ROS generation by MNC fell to 62.4 +/- 16.5 % at 24h and by 48.4 +/- 16.5 % (p<0.001) by 48h. The level of p47(phox) subunit, an ind ex of NADPH oxidase, the enzyme converting molecular oxygen to superoxide ( O-2(.)-) radical, also fell in parallel. Plasma o-tyrosine/phenylalanine ra tio fell significantly from 0.326 +/- 0.053 mmol/mol to 0.303 +/- 0.055 mmo l/mol at 48h and m-tyrosine/phenylalanine ratio fell from 0.363 +/- 0.063 m mol/mol to 0.340 +/- 0.064 mmol/mol (p<0.05). Thus, a 48h fast may reduce R OS generation, total oxidative load and oxidative damage to amino acids.