Chemical pathology of diamino acid deficiency: considerations in relation to lysinuric protein intolerance.

Young rats were force-fed a lysine + arginine-devoid diet or a complete diet for 3 days, and selected biochemical and morphologic studies were conducted. Rats force-fed the experimental diet in comparison with those force-fed the control diet for 3 days showed decreased body weight gain, hepatomegaly with periportal fatty liver, pancreatic and splenic atrophy, and enhanced 14C-leucine incorporation into hepatic proteins. Differences in the experimental animals were observed in the free amino acid levels of serum (decreased lysine, arginine, and ornithine) and liver (decreased ornithine), in blood chemistries (decreased levels of ammonia N2, uric acid, cholesterol, protein, albumin, alkaline phosphatase, LDH and SGOT) and in hematologic findings (leukocytopenia and thrombocytopenia after a morning feeding). The experimental findings in young rats force-fed the lysine + arginine-devoid diet were compared with those reported to develop in children with lysinuric protein intolerance (LPI), an autosomal recessive defect in diamino acid transport. Children with LPI as described by others reveal a number of similarities as well as a number of differences in comparison to the findings in the experimental animals. The comparison suggests that some of the pathological manifestations of LPI may be related to a deficiency of diamino acids but others must be due to different alterations in this complex human disease.