Relationship Between Metabolism Of Pyophosphate And Disorder Of Bone And Mineral Metabolism In Patient With ESRD

Pyrophosphate (PPi) is a known inhibitor of hydroxyapatite formation and has been shown to inhibit medial vascular calcification in vitamin D–toxic rats. It was demonstrated recently that endogenous production of PPi prevents calcification of rat aorta that are cultured in high concentrations of calcium and phosphate. To determining whether PPi metabolism is altered in ESRD and hemodialysis patients, plasma levels PPi and its relative metabolic enzymes, namely nucleotide pyrophosphohydrolase(NTPPPH) and alkaline phosphatase(ALP) were measured in the ESRD and stable hemodialysis patients. And the relationship between the metabolism of PPi and the disorders of bone and mineral were analyzed. The serum [PPi] was 1.99±0.14μmmol/ml in 38 clinically stable hemodialysis patients and 2.08±0.23μmmol/ml in 28 uremia patients compared with 2.00±0.17μmmol/ml in 22 normal subjects (P > 0.05, P < 0.05, respectively). The serum NTPPPH activity was 23.84±4.18 U/ml in 38 clinically stable hemodialysis patients and 21.61±5.18 U/ml in 28 uremia patients compared with 20.34±5.24 U/ml in 22 normal subjects (P <0.01, P > 0.05, respectively). The ALP was highest in hemodialysis patients, uremia patients took second place compared with normal subjects. (P <0.05, P < 0.05, respectively). There was a inverse correlation between PPi level and NTPPPH.(r=-0.35)A positive relationship was observed between NTPPPH activity and serum P and Ca×P. (r=0.30,r=0.31, repectively)。It is concluded that a higher serum [PPi] was observed in uremia patients compared with hamodialysis patients and normal subjects, and the reason was unknown. The relationships between serum NTPPPH activity and serum [PPi] and P, Ca×P suggesting that NTPPPH could contribute to ectopic calcification by coacting with ALP.