Systemic disorders of calcium dynamics in rats with adenine-induced renal failure: Implication for chronic kidney disease-related complications

Aim:   Chronic kidney disease (CKD) causes the dysregulation of systemic mineral metabolism. A major issue in CKD patients is the emergence of ectopic calcification in soft tissues, presumably due to increased levels of calcium (Ca) or inorganic phosphorus (Pi); however, the precise mechanisms have not been fully elucidated. Therefore, this study aims to evaluate Ca dynamics in an animal model of CKD.
Methods:   Renal failure was produced in rats by feeding an adenine-containing diet for 4 weeks, and time-course changes in biochemical parameters, including Ca, Pi, creatinine (Cr), blood urea nitrogen (BUN), parathyroid hormone (PTH), 1,25-dihydroxyvitamin D₃, and N-telopeptide and cross-linked collagen type I (NTx), were monitored once a week during the feeding period. Intestinal absorption, tissue contents, and urinary excretion of Ca were monitored using radioisotope (RI) ⁴⁵Ca.
Results:   Adenine-fed rats exhibited renal failure, ectopic calcification and altered serum parameters, including elevated levels of serum Pi, Cr, PTH and BUN. Serum Ca levels were not increased in rats with renal failure. RI-based experiments revealed that abnormal Ca dynamics including attenuated intestinal absorption, increased incorporation into soft tissues, particularly aortic tissue, in which it was increased threefold, and enhanced urinary excretion occurred in renal failure rats.
Conclusion:   Rats with renal failure induced by an adenine diet exhibited severe abnormality of Ca dynamics, including Ca shortage and ectopic accumulation of Ca. These findings would provide useful information to research CKD-related complications.