Cystine and amino acid concentrations in the urine of pet ferrets (Mustela putorius furo)

Background: The prevalence of cystine urolithiasis in domestic ferrets (Mustela putorius furo) has increased dramatically in the past decade. Genetic mutations associated with a defect in the active resorption of cysteine (which is oxidized to cystine) and dibasic amino acids in the proximal renal tubules leading to cystinuria were described in several species; however, the etiology in ferrets is unknown. This study aimed to characterize cystinuria in pet ferrets. Methods: Urine samples were aseptically acquired from 27 domestic client-owned ferrets with known dietary and medical histories. The samples underwent a routine urinalysis and microscopic evaluation. Urine aliquots were deproteinized with 6% sulfosalicylic acid and analyzed for amino acid concentrations by ion exchange chromatography. Results: Urine cystine concentrations ranged from 8 to 2486 nmol/mL (median 243; SD 540.02). Principal component analyses revealed correlations among urinary amino acid concentrations, which were explained mostly by three components. Analyses revealed significant correlations between cystine and citrulline, ornithine, and lysine concentrations. Linear regression revealed a negative correlation between age and urinary cystine concentrations and no significant correlation between cystinuria and diet or treats. Conclusions and clinical relevance: This is the 1stdescription of urine amino acid analysis in a cohort of pet ferrets. The detected correlations between cystine, ornithine, and citrulline could indicate that the pathology responsible for cystine urolithiasis in ferrets is like in other species. Result may indicate young ferrets are at increased risk of cystine urolithiasis Further research is needed to evaluate the possible association between diet and cystinuria.