Effects of restriction of amino acid supply to the isolated perfused guinea-pig mammary gland.

When individual essential amino acids were omitted for periods of 40--100 min from the infusate substrate solution in isolated perfused guinea-pig mammary gland experiments, uptake of methionine, tyrosine, phenylalanine, histidine and tryptophan (group 1) was significantly depressed by a mean of 49.8%, whereas the remaining essential amino acids (group 2) showed no significant decrease in uptake. During depletion periods oxidation of [14C]amino acids was increased. The possible significance of the differences in absorption between the 2 groups of amino acids is discussed.