INTER-ALPHA-INHIBITOR IN CALCIUM STONES

1. A broad spectrum of proteins has been detected within calcium stone s. A newcomer to the field of urolithiasis is the blood protein inter- alpha-inhibitor. Inter-alpha-inhibitor comprises three protein chains linked by chondroitin sulphate: two heavy chains, H1 (65 kDa) and H2 ( 70 kDa) and a light chain (approx. 30 kDa) most commonly known as biku nin. The physiological function of the two heavy chains is unknown; no r has their presence been reported in urine. However, bikunin has been implicated in various renal diseases, including urolithiasis. 2. This study was undertaken to determine which chains of inter-alpha-inhibit or are actually present in calcium kidney stones. Organic extracts wer e obtained from 10 calcium stones and analysed by SDS/PAGE and Western blotting. The H1 and H2 chains of inter-alpha-inhibitor were detected in 9 of the 10 stones, but only one stone contained a protein with a molecular mass close to that of bikunin (30-35 kDa). 3. These results demonstrate for the first time that H1 and H2 are present in stones an d show that the bikunin chain of inter-alpha-inhibitor may not be the only part of the molecule implicated in stone formation.