Increased binding of quinidine to serum albumin and lipoproteins in anuric rats.

The purpose of this work was to identify the main quinidine binding molecules of rat serum and those macromolecules responsible for increased quinidine binding in serum from rats with acute anuria. Rat sera were fractionated by gel filtration, ultracentrifugation and anion exchange chromatography. The binding of quinidine to sera and serum fractions was determined by equilibrium dialysis. The experiments demonstrated that albumin and lipoproteins are the main quinidine binding molecules in serum from normal and anuric rats. The increased binding by serum from anuric rats is due to both serum lipoproteins and albumin, even though the concentration of albumin is decreased from 2.8 to 1.7 g/100 ml. The increased binding to albumin may be due to conformation changes induced by endogenous substances. The increased binding to lipoproteins may be caused by an increased concentration of pre-beta-lipoprotein.