EFFECTS OF PROTEIN, METHIONINE, OR CHLORIDE ON ACID-BASE-BALANCE AND ON CYSTEINE CATABOLISM

Metabolism of cysteine to sulfate results in production of H+, whereas metabolism of cysteine to taurine does not. Rats were fed a basal low -protein dieter a diet with excess protein, methionine, or chloride fo r 2-3 wk, and effects of these treatments on acid-base homeostasis and on cysteine metabolism were determined. Hepatocytes from rats fed die ts with excess methionine, but not from rats fed diets with excess pro tein or chloride, catabolized a high proportion of cysteine to taurine (32% vs. 4-7% for other groups), and intact rats fed excess methionin e excreted more sulfur as taurine (51% of total sulfur vs. 1-6% for ot her groups). The formation of taurine vs. sulfate as the end product o f cysteine catabolism provides a metabolic compensation that minimizes the acid load in rats fed excess sulfur amino acids. However, increas ed production of taurine vs. sulfate is not a general adaptive respons e to acidogenic diets.