ENHANCED RENAL VITAMIN-K-DEPENDENT GAMMA-GLUTAMYL CARBOXYLASE ACTIVITY IN EXPERIMENTAL RAT UROLITHIASIS

Objective: To detect the role of the enzyme gamma-glutamyl carboxylase in an experimental stone-forming condition. Methods: Urolithiasis was induced in experimental rats by (i) oral feeding of 1% ethylene glyco l (EG) and (ii) feeding a calculus-producing diet containing 3% sodium glycolate. Results: A significant enhancement in the activity of rena l vitamin-K-dependent gamma-glutamyl carboxylase was observed in both groups of experimental urolithic rats. Dicoumarol as well as EG treatm ent enhanced the accumulation of the endogenous substrate for the enzy me. The carboxylase activity was stimulated by sodium oxalate as well as calcium oxalate in vitro. A positive correlation was observed betwe en lipid peroxidation and the renal gamma-glutamyl carboxylase activit y. Conclusion: The enhanced carboxylase activity observed in the hyper oxaluric condition is suggested to be due to stimulation of the enzyme by oxalate/ calcium oxalate, increased concentration of endogenous ca rboxylase substrate and lipid peroxidation.