Serum concentrations of 1,25-dihydroxycholecalciferol and 25-hydroxycholecalciferol in clinically normal dogs and dogs with acute and chronic renal failure

Abstract

Objective - To compare serum concentrations of 1,25-dihydroxycholecalciferol (1,25-[OH]2D3) and 25-hydroxycholecalciferol (25-[OH]D3) in healthy control dogs and dogs with naturally occurring acute renal failure (ARF) and chronic renal failure (CRF). Animals - 24 control dogs, 10 dogs with ARF, and 40 dogs with CRF. Procedure - Serum concentrations of 1,25-(OH)2D3 were measured by use of a quantitative radioimmunoassay, and serum concentrations of 25-(OH)D3 were measured by use of a protein-binding assay. Results - Mean ± SD serum concentration of 1,25-(OH)2D3 was 153 ± 50 pmol/L in control dogs, 75 ± 25 pmol/L in dogs with ARF, and 93 ± 67 pmol/L in dogs with CRF. The concentration of 1,25-(OH 2D3 did not differ significantly between dogs with ARF and those with CRF and was in the reference range in most dogs; however, the concentration was significantly lower in dogs with ARF or CRF, compared with the concentration in control dogs. Mean ± SD concentration of 25-(OH)D3 was 267 ± 97 nmol/L in control dogs, 130 ± 82 nmol/L in dogs with ARF, and 84 ± 60 nmol/L in dogs with CRF. The concentration of 25-(OH)D3 was significantly lower in dogs with ARF or CRF, compared with the concentration in control dogs. Conclusions and Clinical Relevance - The concentration of 1,25-(OH)2D3 was within the reference range in most dogs with renal failure. Increased serum concentrations of parathyroid hormone indicated a relative deficiency of 1,25-(OH)2D3. A decrease in the serum concentration of 25-(OH)D3 in dogs with CRF appeared to be attributable to reduced intake and increased urinary loss.