Model development of hydroxyproline induced hyperoxaluria in young growing pigs

Aim of the study. In this study, we sought to create a model of reversible hyperoxaluria in pigs by feeding with hydroxyproline (HP). Materials and methods. The experiment included 12 pigs divided into 2 groups (n = 6). The pigs were fed twice a day. At the beginning of the experiment, in the adaptation period, all pigs were given standard feed. In the next 7 days, an increasing amount of hydroxyproline (1–3% HP), was added to the feed. In next 14 days, 4% HP was administered in each pig meal. After 14 days of 4% HP diet, the pigs were randomly divided into 2 groups. For 6 pigs, 4% HP treatment had been continued for the next 14 days while the second group of pigs for the next 14 days received a standard HP free diet. 24h urine samples, blood and fecal samples were collected on particular days. Results. The addition of HP to the diet increased urinary oxalate excretion. A characteristic increase was noted after 12 days of treatment with 4% HP. During the removal period, oxalate excretion decreased in the group without HP in diet, while in the group which continued with a 4% HP diet, oxalate excretion significantly increased. Gross examination of kidneys showed that in the group which had 4% HP diet for 4 weeks, kidneys were fibrotic with enlarged cavities, and had small visible urinary stones. In second group, kidneys were relatively normal looking with no visible stones. Conclusion. Hyperoxaluria is reversible, if HP is removed 14 days after the start of 4% HP diet. Prolonged exposure up to 4 weeks causes pathologic changes in kidneys including crystals, sand and small stone formation.