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  • Title: Binding of etiopurpurin and tin-coordinated etiopurpurin to human plasma proteins. Delivery in cremophore EL and dimethyl sulfoxide (paper II).
    Author: Kongshaug M, Cheng LS, Moan J, Morgan AR.
    Journal: Int J Biochem Cell Biol; 1995 Jan; 27(1):71-87. PubMed ID: 7757884.
    Abstract:
    Purpurins are potent hydrophobic photosensitizers in vivo. Cremopfore EL is an important vehicle for the administration of hydrophobic drugs. Mode-delivery-effects on the binding of etiopurpurin (ET2) to human plasma (LDL, HDL, and high density proteins, HDP) is studied for delivery in CRMaq and in DMSO by ultracentrifugation. A similar study of SnET2 is available (Kongshaug et al., 1993) and has been extended. In the absence of plasma, only nonfluorescent ET2 entities (aggregates) were present, a portion of which moved unaffected by gravity (small aggregates), the remainder according to their densities (high density aggregates). Aggregated ET2 showed, at high salt density, similar positions and halfwidths in the gradient, and similar adsorption properties as the aggregates in plasma-containing samples. In CRMaq (1 mg CRM/ml) the adsorptive loss of the dye affected only marginally the binding of fluorescent monomeric ET2. In this mode (i) 20% of ET2 was bound as monomers, about 70% of which to CRM-modified LDL, most of the remainder to CRM-modified HDL; (ii) such HDL also marginally bound small aggregates; (iii) only monomeric ET2 was bound to CRM-modified LDL. In delivery in DMSO, aggregated ET2 (98% of ET2 in the gradient) converted, post centrifugally, into minor amounts of HDL-bound monomeric ET2; LDL-bound ET2 included monomers (about 50%) and small aggregates, mainly dimers. The percentage binding of SnET2 to HDP was independent of the concentrations of CRMaq and HDL. Plasma-bound small aggregates (such as dimers) and plasma-unbound high density aggregates (mean densities of 1.13-1.19 g/ml) were substantially present in the plasma-containing samples. There were mode-delivery-effects upon the yields and properties of aggregated ET2, and upon the yields of plasma-bound monomeric ET2. Monomeric ET2 showed a remarkably high percentage binding to LDL and was similarly distributed among the lipoproteins as is total cholesterol. There was little or no real mode-delivery-effect upon the distribution of monomeric ET2 among the plasma proteins. The affinity of CRM-modified LDL for SnET2 was similar to that of HDL plus HDP in native plasma.
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