Kinetic characteristics of porphyrin distribution in the blood

The objectives of the present work were to compare the kinetics of porphyrin exchange between different plasma lipoproteins and biological membranes. Isolated proteins were loaded by porphyrins (chlorin e6 derivatives and Zn- phthalocyanine) and the kinetics of pigment transfer from protein carrier to pigment-free proteins or biological membranes were analyzed by spectroscopic techniques. It was obtained that the rate of exchange depended strongly on the pigment polarity. A main trend was that the time required for equilibrium redistribution increased with decreasing dyes polarity. Its values changed from seconds for polar sensitizers to tens of minutes in the case of apolar dyes. Extremely slow redistribution (several hours) was observed when the recovery of apolar pigments (chlorin e6 trimethylester and Zn-phthalocyanine) from LDL was studied. The results clear indicate that the rate of pigment exchange between proteins and cells may contribute to the control of sensitizer distribution in blood and solid tissues.