Abstract
The purpose of the study was to compare biodistribution profiles and elimination pathways of DOTA-Tyr(3)-octreotate (DOTA-TATE) and DOTA-1-Nal(3)-octreotide (DOTA-NOC) radiolabelled with In-111 in rats. Both In-111 radiolabelled peptides showed high and comparable rates of internalization into AR42J rat pancreatic carcinoma cells in agreement with their similar affinity to somatostatin receptor subtype sstr2.
Both peptides also exhibited similar distribution profiles in rats. High radioactivity uptake in somatostatin receptor-rich organs and in the kidney was determined.
Due to higher lipophilicity of 111In-DOTA-NOC its plasma protein binding was higher, the blood radioactivity decrease was slightly slower and liver accumulation was significantly higher in comparison with 111In-DOTA-TATE. The physiological internalization of radioactivity into somatostatin receptor-rich organs (the panceas and adrenals) was for 111In-DOTA-NOC about twice of that for 111In-DOTA-TATE.