Trabecular bone remodeling and bone mineral density in the adult cat during chronic dietary acidification with ammonium chloride.

Ammonium chloride (NH4Cl) is used as a urinary acidifier in the treatment and prevention of feline urologic syndrome. It is reported to cause alterations in calcium and bone metabolism in humans, dogs, and rats. Adult cats with normal renal function were fed 1.5% NH4Cl for 6 months to study the effects of chronic dietary acidification on trabecular bone remodeling of the iliac crest and bone mineral density (BMD) of lumbar vertebral trabecular bone and femoral cortex. Histomorphometric analyses of iliac crest biopsies were performed before and after treatment. Static and dynamic parameters of bone resorption and formation were determined. Single-energy quantitative computed tomography (SEQCT) was used to measure lumbar trabecular and femoral cortical BMD. There were no significant treatment effects in iliac crest trabecular bone remodeling or BMD of the vertebrae and femora. Bone remodeling activity decreased with time in both acidotic and control cats. Vertebral BMD increased with time in both groups of cats, whereas no change was seen in the femora. Thus, chronic dietary acidification for 6 months with therapeutic levels of NH4Cl produced no significant changes in trabecular bone remodeling or bone mineral density in adult cats.