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in Rats Fed a Low Protein Diet1
Institute of Human Nutrition, University of Southampton, Southampton SO9 3TU, U.K.
Plasma taurine and serine decrease following trauma and in severe inflammatory disease. These changes may signify an increase in requirements for sulfur amino acids. We previously demonstrated that cysteine supplementation can restore the impaired ability of rats fed an 8% casein diet to increase hepatic zinc, glutathione (GSH) and protein concentrations in response to tumor necrosis factor
(TNF
). Here we examined whether serine or taurine produces a similar effect, because serine provides the carbon skeleton of cysteine and taurine is its major metabolite. After 7 d of receiving either a 20% casein diet supplemented with cysteine or an 8% casein diet supplemented with alanine, serine or taurine, rats received an intraperitoneal injection of human TNF
. Tumor necrosis factor caused no change in hepatic GSH but resulted in a lower GSH concentration in lung in rats fed the alanine-supplemented diet. Neither taurine nor serine increased liver GSH relative to that in rats fed alanine, but the depression in lung due to TNF injection was lessened. The absolute increase in ceruloplasmin in response to TNF was enhanced in rats fed the alanine-supplemented diet relative to those fed the 20% casein diet. Serine normalized this response. This observationthe effects of taurine and serine on lung GSH and a significant negative correlation between ceruloplasmin and liver and lung GSH concentration in rats fed TNFsuggests that supplemental serine and taurine may improve antioxidant defenses when dietary supplies of cysteine are low but do not influence cysteine availability for a normal response to TNF.
KEY WORDS: tumor necrosis factor taurine serine rats
1 The authors are grateful to the Geoffrey Taylor Memorial Fund for financial assistance to C. Pathirana.
2 To whom correspondence should be addressed.
Manuscript received 29 October 1991. Revision accepted 6 March 1992.