Partitioning and thermodynamics of dipyridamole in the n-octanol/buffer and liposome systems.
The thermodynamics of partitioning (K) of dipyridamole has been determined in n-octanol/buffer and liposome-buffer systems at pH 7.4. Dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) were used to prepare multilamellar liposomes. Partitioning of dipyridamole did not depend on the amount of n-octanol employed, however, partitioning was dependent upon the quantity of DMPC employed to prepare liposomes. Plots of log K vs 1/T were linear in the n-octanol and liposome systems. Partitioning was generally greater in liposomes than in the n-octanol/buffer system. Among liposomes, the partitioning was greater in DMPC liposomes at all temperatures. The values of enthalpy (delta H) and entropy (delta S) were positive in both the n-octanol and liposome systems. These values were lower in DMPC liposomes and were comparable in the n-octanol and DPPC liposomes. Thus, the interaction of dipyridamole depends on the rigidity of lipid bilayers and liposomes constitute a more selective partitioning system than the n-octanol/buffer system.
Betageri
G V
GV
Department of Pharmacal Sciences, School of Pharmacy, Auburn University, AL 36849-5503.
Dipali
S R
SR
D002021:Buffers; D004176:Dipyridamole / Q000737:chemistry*; D008081:Liposomes; D000442:Octanols; D010743:Phospholipids / Q000737:chemistry; D012995:Solubility; D013696:Temperature; D013816:Thermodynamics
D002021:Buffers; D008081:Liposomes; D000442:Octanols; D010743:Phospholipids; D004176:Dipyridamole