Detection of osteopontin as matrix protein in calcium-containing urinary stones

Abstract

蓚酸カルシウム, リン酸カルシウム, 尿酸, リン酸マグネシウムアンモニウムの4種類の結石内マトリックスを, Stains-All染色によりトロンビン分割の有無でオステオポンチン(OPN)の存在を確認した.マトリックス成分は0.1M EDTA溶液で抽出した.その上N末端より20残基のアミノ酸分析を施行した.蓚酸カルシウム, リン酸カルシウムのみOPNが存在し尿酸, リン酸マグネシウムアンモニウム結石内には認めなかった.骨のマトリックスとして骨形成に関わり, 強固にヒドロキシアパタイトと結合するOPNが, カルシウム含有結石形成過程においても重要である

Osteopontin (OPN) has been identified as a matrix protein of calcium oxalate urinary stones by sequencing c-DNA for urinary stone protein. OPN, a phosphoprotein, is susceptible to thrombin digestion and specifically stainable with Stains-All. We examined the matrix in 4 kinds of urinary stones, calcium oxalate dihydrate, calcium phosphate, magnesium ammonium phosphate and uric acid; for the presence of OPN by staining thrombin-digestion and undigested matrix with Stains-All. Matrix was extracted with a 0.1 M ethylenediamine tetraacetic acid (EDTA) solution. Furthermore, the amino acid sequence was determined for the NH2-terminal 20 amino acid residues. OPN was identified in calcium oxalate dihydrate and calcium phosphate stones, but was absent in magnesium ammonium phosphate and uric acid stones. Our findings suggest that OPN, which binds tightly to hydroxyapatite and is related to bone formation as bone matrix, also participates in the formation of calcium-containing urinary stones.