Binding of ¹¹¹In-DTPA-Octreotide, ¹¹¹In-DOTA-Octreotide and ⁸⁸Y-DOTA-Tyr³-Octreotide to Plasma Proteins

Joshita Djajadisastra¹ (djaja@faf.cuni.cz), Alice Lázníčková¹, Helmut R. Mäcke²

¹Department of Biophysics, Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Czech Republic
²Department of Nuclear Medicine, Kantonhospital Basel, Switzerland

Summary

Binding of three somatostatin receptor-specific peptides, namely ¹¹¹In-DTPA-octreotide, ¹¹¹In-DOTA-octreotide and ⁸⁸Y-DOTA-Tyr³-octreotide, to human, bovine, and rat plasma proteins was determined by equilibrium dialysis at 37 °C and by ultrafiltration at room temperature. It was shown that these somatostatin receptor specific peptides are only slightly bound to plasma proteins (per cent bound < 55 %). Interspecies differences in the degree of binding to plasma proteins are negligible. The ultrafiltration method using cellophane bag gave almost similar results comparing to equilibrium dialysis method, the only disadvantage of this method is the need to a greater amount of plasma. The binding of the receptor-specific peptides under study will exert only small effect on their pharmacokinetics.