Influence of dietary cystine on intestinal absorption and tissue distribution of methionine in the chick.
Studies were conducted on intestinal absorption and tissue distribution of methionine by chicks fed a crystalline amino acid diet containing .2% DL-methionine and .2 or .4% L-cystine or L-cysteine. Chicks fed the higher level of cystine or cysteine had previously been shown to exhibit depressed growth as opposed to chicks fed the lower level of these amino acids. In two experiments, 35S radioactivity of whole plasma and the protein and supernatant fractions were compared among chicks fed the different treatments at 30 or 60 min after oral intubation of L-[35S]-methionine into the crops. When the data were analyzed factorially, a significant level effect was noted for whole plasma and the protein and supernatant fractions, all of which were higher for chicks fed .2% L-cystine than those fed .4% L-cystine. Results with chicks fed the two levels of L-cysteine generally agreed with those of chicks fed L-cystine, although the differences were not as great. The labeled methionine was also added to diets containing .2 or .4% L-cystine of meal-fed chicks. Higher levels of radioactivity were observed in the liver but not in muscle or plasma of chicks fed the lower level of cystine at 7 hr after oral consumption of the isotope. No significant differences in liver, muscle, or plasma radioactivity were noted in a fourth experiment between chicks fed .2 or .4% L-cystine at 24 hr after intraperitoneal injection of L-[35S]-methionine. In vitro studies showed no differences in methionine accumulation by isolated intestinal segments incubated with three levels of cystine.
D000818:Animals; D002645:Chickens / Q000378:metabolism*; D003553:Cystine / Q000494:pharmacology*; D007408:Intestinal Absorption / Q000187:drug effects*; D008715:Methionine / Q000378:metabolism*
D003553:Cystine; D008715:Methionine