Effect of Plasma Protein Binding on Kinetics of PN 200‐110 in the Isolated Perfused Rat Heart

Abstract

The myocardial accumulation and elimination pharmacokinetics of PN 200-110 (PN) were investigated in the single pass isolated perfused rat heart by two methods. A direct method, radioactivity measurement in myocardial tissue after various perfusion times, and an indirect method, concentration determination in coronary effluent, by fractionary collection of samples, during infusion and elimination periods. Both methods showed that the myocardium could be considered as a one-compartment model with regard to PN pharmacokinetics. The perfusion with a modified Krebs-Ringer (MKR) solution containing 1 nM of (+/-)PN 200-110 and [3H]-(+)PN 200-110 as radioactive tracer, led to an accumulation of about 61.4 fmol.mg-1 myocardial tissue at steady-state. The effect of protein binding on the uptake and pharmacokinetic parameters of PN has been investigated in this isolated perfused heart (IPH) model. binding of PN decreased as a function of increasing bovine serum albumin (BSA) levels in the perfusion solution. As a matter of fact, the mean steady state myocardial concentration of PN was decreased by 42.9, 56.2, 76.5, 83.9 and 95.5% for respectively, 1, 2.5, 6, 10 and 40 g.l-1 of BSA. In the same way, the free fraction, the apparent volume of distribution (Vd) and the distribution and elimination half-lives were decreased. On the contrary, the elimination rate constant was increased.