High dietary protein and taurine increase cysteine desulfhydration in kittens

The objective of this study was to determine the effect of dietary protein and taurine on cysteine desulfhydration in various kitten tissues. Cysteine desulfhydration was assessed in liver, kidney, skeletal muscle, heart, spleen, brain and jejunum of kittens fed one of the following diets for 5 wk: 20% protein, 0% taurine diet (LPOT); 20% protein, 0.15% taurine diet (LPNT); 60% protein, 0% taurine diet (HPOT); and 60% protein, 0.15% taurine diet (HPNT). Cats fed LPOT and HPOT had been fed a taurine-free diet for 10 wk before the 5-wk experiment. The activity of cysteine desulfhydration was determined by measuring the production of H₂ ³⁵S from ³⁵S-cysteine in the presence and absence of α-ketoglutarate (αKG) in the incubation medium. Liver and kidney had the highest total activities among the tissues tested (P < 0.01). Total hepatic desulfhydration activities [μmol H₂S/(min · kg body wt)] in cats fed LPOT, LPNT, HPOT and HPNT were (mean ± SEM) 117 ± 6, 135 ± 10, 137 ± 10 and 190 ± 9, respectively. Dietary taurine had a significant effect on activity when expressed per gram liver (P < 0.01), per gram protein (P < 0.05) and per kilogram body weight (P < 0.001). Dietary protein had a significant effect (P < 0.001) only when activity was expressed relative to body weight because of the significant effect of protein on relative liver weight. The direct pathway via cysteine desulfhydrase appears to be the major route of cysteine desulfhydration in kitten liver because the values obtained in the absence of αKG were 81-88% of those obtained in the presence of αKG.