Activity and expression of vitamin K-dependent gamma-glutamyl carboxylase in patients with calcium oxalate urolithiasis.

OBJECTIVES

To evaluate the correlation between vitamin K-dependent gamma-glutamyl carboxylase (GGCX) and the formation of calcium oxalate urolithiasis (COU).

METHODS

Renal cortex samples were obtained from patients undergoing nephrectomy and divided into 3 groups: (1) urolithiasic group (n = 44); (2) hydronephrosis-without-stone group (control group A, n = 6), and (3) normal control group (control group B, n = 21). Immunohistochemical technique was established to study the location of GGCX in renal tissues. The carboxylase activity was detected by the isotope-labeled carboxylatic reaction in vitro. We also quantified GGCX mRNA levels using TaqMan real-time reverse-transcription PCR, and protein was detected by Western blot.

RESULTS

GGCX was located in the cytoplasm of renal tubular epithelial cells and the activity of GGCX in the urolithiasic group was significantly decreased compared with that of controls (p < 0.05). GGCX mRNA in the urolithiasic group was lower than that in the normal control group, which was on average 7.86-fold underexpressed in the urolithiasic group compared to the normal control group. Protein expression of GGCX in the urolithiasic group (27.64 +/- 0.29) was weaker than that in the other 2 control groups (control group A 55.22 +/- 0.36, control group B 53.78 +/- 0.33), p < 0.05.

CONCLUSIONS

The activity and expression of GGCX are decreased in renal tissues of patients with COU.