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1Medical and Molecular Genetics Center, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet de Llobregat; 2Genetic Unit, Department of Physiology II, Universitat de Barcelona-IDIBELL; 3Centre for Biomedical Research on Rare Diseases (CIBERER-U730); and 4Epidemiology and Cancer Registry Unit, ICO-IDIBELL, L'Hospitalet de Llobregat, Barcelona; 5Molecular Nutrition Unit, Technical Univeristy of Munich, Freising, Germany; and 6Animal Facility Service, IRO-IDIBELL, L'Hospitalet de Llobregat; 7Department of Biochemistry and Molecular Biology, Universitat de Barcelona; 8Parc Científic de Barcelona; and 9CIBERER-U731, Barcelona, Spain
Submitted 13 March 2007 ; accepted in final form 15 June 2007
Cystinuria is a hereditary disorder caused by a defect in the apical membrane transport system for cystine and dibasic amino acids in renal proximal tubules and intestine, resulting in recurrent urolithiasis. Mutations in SLC3A1 and SLC7A9 genes, that codify for rBAT/b0,+AT transporter subunits, cause type A and B cystinuria, respectively. In humans, cystinuria treatment is based on the prevention of calculi formation and its dissolution or breakage. Persistent calculi are treated with thiols [i.e., D-penicillamine (DP) and mercaptopropionylglycine (MPG)] for cystine solubilization. We have developed a new protocol with DP to validate our Slc7a9 knockout mouse model for the study of the therapeutic effect of drugs in the treatment of cystine lithiasis. We performed a 5-wk treatment of individually caged lithiasic mutant mice with a previously tested DP dose. To appraise the evolution of lithiasis throughout the treatment a noninvasive indirect method of calculi quantification was developed: calculi mass was quantified by densitometry of X-ray images from cystinuric mice before and after treatment. Urine was collected in metabolic cage experiments to quantify amino acids in DP-treated and nontreated, nonlithiasic mutant mice. We found significant differences between DP-treated and nontreated knockout mice in calculi size and in urinary cystine excretion. Histopathological analysis showed that globally nontreated mutant mice had more severe and diffuse urinary system damage than DP-treated mice. Our results validate the use of this mouse model for testing the efficacy of potential new drugs against cystinuria.
D-Penicillamine treatment; cystinuria model; calculi; noninvasive imaging system
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