Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Somatostatin receptor-positive human tumors can be detected using radioiodinated analogues of somatostatin, both in vitro and in vivo. [123I-Tyr3]-octreotide has been successfully used in the visualization of somatostatin receptor-positive tumors by gamma camera scintigraphy, but this radiopharmaceutical has some major drawbacks, which can be overcome with other radionuclides such as 111In. As starting material for a potentially convenient radiopharmaceutical, a diethylenetriaminopentaacetic acid (DTPA) conjugated derivative of octreotide (SMS 201-995) was prepared. This peptide, [DTPA-D-Phe1]-octreotide (SDZ 215-811) binds more than 95% of added 111In in an easy, single-step labeling procedure without necessity of further purification. The specific somatostatin-like biologic effect of these analogues was proven by the inhibition of growth hormone secretion by cultured rat pituitary cells in a dose-dependent fashion by octreotide, [DTPA-D-Phe1]-octreotide and non-radioactive [115In-DTPA-D-Phe1]-octreotide. The binding of [111In-DTPA-D-Phe1]-octreotide to rat brain cortex membranes proved to be displaced similarly by natural somatostatin as well as by octreotide, suggesting specific binding of [111In-DTPA-D-Phe1]-octreotide to somatostatin receptors. The binding of the indium-labeled compound showed a somewhat lower affinity when compared with the iodinated [Tyr3]-octreotide, but indium-labeled [DTPA-D-Phe1]-octreotide still binds with nanomolar affinity. In conjunction with in vivo studies, these results suggest that [111In-DTPA-D-Phe1]-octreotide is a promising radiopharmaceutical for scintigraphic imaging of somatostatin receptor-positive tumors.
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PMID:[111In-DTPA-D-Phe1]-octreotide, a potential radiopharmaceutical for imaging of somatostatin receptor-positive tumors: synthesis, radiolabeling and in vitro validation. 165 15

Somatostatin (SRIF) receptors are present in a variety of human tumors such as pituitary and endocrine pancreatic tumors, brain tumors, small cell lung cancers and malignant breast tumors. The 111In-labeled SRIF analog SDZ 215-811 (OctreoScan 111) binds with a high affinity to somatostatin receptors and exhibits SRIF-like biological properties, as demonstrated by the inhibition of growth hormone release from pituitary cells. We report here the in vitro characterization of SDZ 215-811 and the in vivo imaging of an islet cell tumor grown in rats using [111In]SDZ 215-811. In vitro autoradiographies revealed a high density of SRIF receptors on the pancreatic tumor tissue. As early as 5 min after intravenous injection of [111In]SDZ 215-811 into tumor-bearing rats, the tumors were clearly localized by gamma-camera scintigraphy. Even 24 h post injection, the islet cell tumor was still detectable. The radioligand was mainly cleared from the circulation via the kidneys, with a rapid alpha-phase (t1/2 = 5.6 min) and a slow elimination phase (t1/2 = 7.3 h). Biodistribution studies revealed a relatively high accumulation of radioactivity in the kidneys, but low uptake into the liver and the intestine. High uptake of [111In]SDZ 215-811 was observed for the tumor tissue (0.92 +/- 0.07% ID/g; 1 h post injection). Interestingly, a tumor load of 0.14 +/- 0.01% ID/g was still measured after 24 h. The tumor/blood ratio was 4.93 after 24 h, indicating specific accumulation of radioactivity in the islet cell tumor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:OctreoScan 111 for imaging of a somatostatin receptor-positive islet cell tumor in rat. 839 88