We desired an animal model for prolidase deficiency which reflected the phenotype in humans with this inherited metabolic disorder. The human disorder is characterized by poor wound healing with ulcers on the lower extremities, bony abnormalities and mental retardation. These findings in humans, however, are not consistent. Pedigrees have been described in which siblings with identical biochemical phenotype may have variable clinical manifestations. To pursue these studies, we established a collaboration with Dr. Teresa Gunn of the McLaughlin Medical Research Institute in Great Falls, Montana. She has described a mouse strain (dal/dal) which have abnormalities in coat color. Breeding a colony of homozygous dal/dal mice, she then identified a 4-bp deletion in the pepd gene encoding prolidase. The phenotype in these animals included hypertrophic cardiomyopathy. We established a colony of these mice and since the backgrouind strain was indeterminate, we obtained heterozygotes breeding dal/dal with C3H and obtained F2 animals which were tested for red cell prolidase to determine WT and dal/dal. Litter mates were then used as controls for our studies. Two protocols were carried out. First, wounds were inflicted with a 5 mm punch biopsy. Control wounds were treated with vehicle whereas test wounds were treated with various preparations of a nitric oxide agent (ProliNO) which released proline as well as nitric oxide. We found that the level of ProliNO used was toxic in that it inhibited wound healing. Importantly, there was no observable difference between WT and dal/dal mice. Another protocol we tried is the two-stage skin tumorigenesis model. Again, we found no difference between WT and daql/dal in their production of papillomas. Thus, we had to conclude that under these conditions, prolidaase activity was not a limiting factor. Prolidase is necessary for both proline nutrition and for proline recycling from endogenous protein, However, proline can be endogenously synthesized from either glutamate or ornithine. Our hypothesis is that under the various stress conditions, endogenous proline biosynthesis would be upregulated to compensate for inability to obtain proline from nutritional proteins or from protein recovered from degradation of endogenous proteins. We will test this hypothesis by comparing two periods a period of maximal growth (age 6-8 weeks) and at maturity (age 5 months). They will also be on two different diets, one containing fish meal (regular diet) which contains some free proline and an optional diet containing only plant products.
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