Lecithin-cholesterol acyltransferase (LCAT) activity in chronic uremia.

High plasma concentrations of triglycerides and low plasma concentrations of esterified cholesterol and lysolecithin, with an impaired rate of VLDL and LDL catabolism, have been reported in chronic uremic patients. An important contribution to these abnormalitites might be an impaired activity of the (LCAT). Serum LCAT activity and cholesteryl ester clearance were determined in 11 patients with chronic renal failure and in 10 controls. LCAT activity was determined by using the serum of each patient both as a source of enzyme and as a substrate ("intrinsic" activity) and was compared with the activity determined on a standard substrate ("extrinsic activity), so as to ascertain the presence of inhibitory factors in the patients' sera. Both activityes have been found to be significantly (P less than 0.01) lower in chronic uremic patients than in controls. The cholesteryl ester clearance apparently did not respond to the stimulatory effect of hypertriglyceridemia, as observed in other cases of dislipoproteinemias. The parallel decrease of both enzyme activities makes it unlikely that it is due to the presence of "uremic toxins" inhibiting the enzyme activity. LCAT synthesis in the liver is probably reduced in chronic uremia. These results suggest that in chronic uremia the VLDL fail to cooperate in their own catabolism.