Figure 5.
Examining the role of factors within the DSPC/Chol liposomes that may affect Cu(DDC)2 levels in the plasma compartment 30 min after administration.
Notes: (A) Preparation of Cu(DDC)2 inside DSPC/Chol (55:45) liposomes containing either CuSO4 (•) or Cu-gluconate (▪) as a function of time at 25°C in SH buffer. (B) The percent of injected Cu(DDC)2 dose administered intravenously to CD-1 mice (n=4) remaining in the plasma 30 min after injection. The formulations were prepared at different Cu(DDC)2-to-lipid ratios (0.2, 0.1, and 0.05, mol:mol) and prepared using liposomes with encapsulated CuSO4 or Cu-gluconate buffers. Copper levels were measured by AAS and, after subtraction of background plasma copper levels, these levels were used as a surrogate for Cu(DDC)2. (C) Formation of Cu(DDC)2 inside DSPC/Chol (55:45) liposomes containing CuSO4 with (▪) or without (•) nigericin as a function of time at 25°C. The external buffer for these liposomes was KCl (150 mM) and Histidine (20 mM). (D) The percent injected dose of Cu(DDC)2 injected into CD-1 mice (n=4) remaining after 30 min following iv administration of Cu(DDC)2 prepared in DSPC/Chol liposomes in the presence and absence of nigericin. Copper levels were measured by AAS and, after subtraction of background plasma copper levels, these levels were used as a surrogate for Cu(DDC)2. For panels A and C, n=3 replicate experiments. In panels A and C if the error bars are not visible then the error is within the size of the symbol used. For Panels B and D, n=4 mice per group. All data are plotted as mean ± standard error of the mean.
Abbreviations: AAS, atomic absorption spectroscopy; Chol, cholesterol; DDC, diethyldithiocarbamate; DSPC, distearoyl-sn-glycero-3-phosphocholine; iv, intravenous; SH, sucrose HEPES.