Affinity For Octreotide Research Articles

Octreotide uptake in the head and neck

A 56-YEAR-OLD woman with a history of medullary thyroid carcinoma had a total thyroidectomy in 1968 with subsequent bilateral neck irradiation and then a right neck dissection in 1970. For recurrent disease, a left neck dissection was required in 1975, followed by a right supraclavicular and upper mediastinal dissection in 1980 with consequent lower neck and superior mediastinal irradiation. An octreotide study was performed in efforts to localize recurrent or metastatic medullary thyroid carcinoma. Abnormal uptake just to the right of the skull vertex and within the base of the skull and in the neck in the region of the thyroid gland (Fig 1) was found. Magnetic resonance imaging scan of the brain showed an extra-axial 1.2-cm mass along the fight parietal parasagittal convexity which enhanced uniformly, highly suggestive of a meningioma or possibly a metastases from the patient's known thyroid carcinoma (Fig 2). Magnetic resonance imaging scan of the neck showed a highly vascular right parapharyngeal mass extending from the carotid bifurcation encompassing the fight internal carotid artery with extension into the skull base. On two separate occasions, the parapharyngeal tumor was embolized with Ivalon particles in efforts to reduce its vascularity, before surgical removal. The patient underwent fight neck exploration with excision of the parapharyngeal mass. Pathology confirmed recurrence of medullary carcinoma of the thyroid. A few months later, the right extra-axial mass was surgically removed with pathological confirmation of a secretory meningioma. amine precursor uptake and decarboxylation (APUD) or neuroendocrine tumors have been shown to have an affinity for octreotide and have been described in recent literature. 4 The prime utility for octreotide has been endocrine active tumors of the gastroenteropancreatic system, malignant lymphomas, small cell lung carcinomas, pheochromocytomas, and carcinoid tumors. The complete list however is becoming quite extensive) Both endocrine and nonendocrine neck and cranial tumors are included in the differential for octreotide uptake. Detection for meningiomas by octreotide scanning has shown a 100% sensitivity: -7 Medullary carcinoma of the thyroid has shown a 71% sensitivity for the presence of somatostatin receptors in a recent series. Possible causes of head and neck activity on octreotide scans include the following:

Somatostatin receptors in human prostate and prostate cancer.

Benign as well as malignant human prostatic tissues were evaluated for their content of somatostatin (SRIH) receptors (SRIH-R). In vitro receptor autoradiography techniques on cryostat sections were performed using 125I-labeled [Tyr3]octreotide as well as 125I-labeled [Leu8,D-Trp22,Tyr25]SRIH-28 as radioligands. SRIH-R were identified in all normal and hyperplastic prostates in the smooth muscles of the stroma, whereas the glands did not express the receptors. Muscular nodules were strongly receptor positive as well. The receptors were of high affinity (Kd = 0.4 nmol/L) and high specificity for biologically active SRIH analogs; high affinity for SRIH-14, SRIH-28, and octreotide was detected, suggesting the presence of the SSTR2 receptor subtype. In situ hybridization studies confirmed the presence of SSTR2 messenger ribonucleic acid in these tissues. Primary prostate cancers did not have SRIH-R identified with 125I-labeled [Tyr3]octreotide. However, they were expressing SRIH-R identified with 125I-labeled [Leu8,D-Trp22,Tyr25]SRIH-28, with a high affinity for SRIH-14 and SRIH-28, but low affinity for octreotide. The receptors were located on tumoral cells. In situ hybridization studies revealed a preferential expression of SSTR1. Primary human prostate cancers, therefore, express a different SRIH-R subtype than benign prostate tissue. Several veins and the ganglion cells from the prostatic plexus in the surroundings of the tumors were expressing SRIH-R with high affinity for octreotide as well. These data suggest that the human prostate as well as prostate cancers may be targets for SRIH therapy; however, SRIH analogs with different selectivities for SRIH-R subtypes are required in each case.

Characterization, tissue distribution and biological activity of the novel neuropeptide secretoneurin

other. Each group shows marked sequence similarities in their putative transmembrane spanning regions, whereas the two groups are structurally different from each other. Operational information suggests a similar subdivision, since the pharmacological profiles of SSTRliSSTR4 receptors (virtually no affinity for octreotide, seglitide, RC 160) are markedly different from the profiles of SSTR2/SSTR-3/SSTR-5 receptors (intermediate to very high affinity for these compounds). The previously termed SS1 or SRIF-1 receptors correspond to the SSTR-2 receptors, whereas the SSTR-1 receptor is equivalent to SS-2 and presumably to SRIF-2 receptors (both initially defined by their lack of afIinity for octreotide and seglitide). Transductional information shows that all 5 cloned receptors couple negatively to adenylyl cyclase activity. Since all cloned receptors have similarly high affinity for SRIF14 and -28, the following nomenclature can be proposed: 3 subtypes of SRIF-1 (lA, lB, 1C) receptors (SSTR-2, -5 and -3) and 2 subtypes of SRIF-2 (2A, 2B) receptors (SSTR-1 and -4). Operational, structural and transductional data in support of the present proposal, as well as brain distribution of the different receptors wilI be presented.