Renal handling of matrix Gla-protein in humans with moderate to severe hypertension.

Vascular calcifications are common among patients with hypertension. The vitamin K-dependent protein matrix Gla-protein plays an important role in preventing arterial calcification. Since a decrease in renal clearance is a prevalent clinical problem in patients with hypertension, we aimed to study the renal clearance of matrix Gla-protein from the circulation in these patients having a wide range of creatinine clearances. Ninety moderate to severe hypertensive patients who were scheduled for renal angiography were enrolled in the study. In these patients, renal arterial and renal venous blood was sampled prior to the administration of contrast material in order to determine the total renal and single kidney clearance of matrix Gla-protein. The average renal fractional extraction of matrix Gla-protein was 12.8%. There was no significant correlation between creatinine clearance (range 26-154) and renal fractional extraction of matrix Gla-protein in this population. The extraction of matrix Gla-protein was not influenced by the presence of a renal artery stenosis. In conclusion, we demonstrate that the kidney is able to extract matrix Gla-protein from the plasma at a constant level of 12.8%, independent of renal function in hypertensive subjects.