title: Cysteine metabolism in vivo of vitamin B6-deficient rats.
abstract: The expirations of 14CO2 from DL-[1-14C]-, DL-[3-14C]- and L-[U-14C] cysteine used as isotopic tracers were estimated in order to determine the in vivo metabolic distribution of L-cysteine in pyridoxine deficient rats. The expired 14CO2 from L-[U-14C] cysteine was increased by pyridoxine deficiency. The loading of non-physiological dose of L-cysteine resulted in remarkable increase in the expiration of 14CO2 from each tracer in deficient rats as well as in controls. The in vivo metabolic distributions of L-cysteine were calculated from the expired 14CO2 from these isotopic tracers. The in vivo metabolic distribution of L-cysteine calculated showed that the remarkable lesion in taurine pathway occurred in pyridoxine deficient rats, and when non-physiological dose of L-cysteine was loaded the catabolism of L-cysteine of controls was markedly increased in either pyruvate or taurine pathway, whereas the L-cysteine catabolism in deficient rats was increased only in pyruvate but not in taurine pathway. The urinary excretions of 35S-labeled metabolites such as sulfate or taurine were also examined in deficient and control rats.
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002250:Carbon Radioisotopes; D003545:Cysteine / Q000378:metabolism*; D006207:Half-Life; D007553:Isotope Labeling; D008297:Male; D011773:Pyruvates / Q000378:metabolism; D051381:Rats; D013462:Sulfur Radioisotopes; D013654:Taurine / Q000378:metabolism; D026681:Vitamin B 6 Deficiency / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D011773:Pyruvates; D013462:Sulfur Radioisotopes; D002245:Carbon Dioxide; D013654:Taurine; D003545:Cysteine