Eighty-seven percent of the total cellular pool of somatostatin (SRIF) receptors in pancreatic islets are located intracellularly. Upon glucose stimulation (300 mg/dl) of insulin release, 8-15% of intracellular SRIF receptors are translocated to the plasma membrane. Affinity of SRIF receptors does not change during their migration and the total cellular pool of receptors remains constant. With ...

GH4C1 cells are a clonal strain of rat pituitary tumor cells which synthesize and secrete prolactin and growth hormone. Somatostatin, a hypothalamic tetradecapeptide, inhibits the release of growth hormone and, under certain circumstances, also prolactin from normal pituitary cells. We have prepared [125I-Tyr1]somatostatin (approximately 2200 C1/mmol) and have shown that this ligand binds to a...

Exchange of information occurs between cells of neuroendocrine and immune systems. Neuroendocrine hormones may modulate lymphoid cell activities, including proliferation and mitogenesis, and immune cells may produce neuropeptides as well. Neuropetide Y is synthesized in B-cell leukaemia lymphoblasts, while substance P immunoreactivity has been detected in neoplastic haematological samples of di...

Albumin fusion technology, the combination of small molecular proteins or peptides with human serum albumin (HSA), is an effective method for improving the medicinal values of natural small molecular proteins or peptides. However, comparative studies between HSA-fusion proteins or peptides and the parent small molecules in biological and molecular mechanisms are less reported. In this study, we...

Neuroblastoma is the most common extracranial solid tumor of children. Neuroblastoma tumors derive from the neural crest and synthesize neurotransmitters including the neuropeptide somatostatin. This study was designed to characterize somatostatin receptors both in primary neuroblastoma tumors and in two neuroblastoma cell lines, SKNSH and IMR32. Somatostatin receptors were identified in 6 of 7...

Five somatostatin receptor (sst) subtype genes, sst(1), sst(2), sst(3), sst(4) and sst(5), have been cloned and characterised. The five sst subtypes all bind natural somatostatin-14 and somatostatin-28 with high affinity. Endocrine pancreatic and endocrine digestive tract tumours also express multiple sst subtypes, but sst(2) predominance is generally found. However, there is considerable varia...

The first part of this contribution reviews the current knowledge about endocrine and neuromodulatory actions of somatostatin. These biological actions are exerted according to endocrine, paracrine and autocrine modes of action and involve five distinct types of membrane receptors belonging to the 'super-family' of G-protein-coupled receptors. A new concept concerning a juxtacrine mode of actio...

Somatostatin agonists are rapidly and efficiently internalized with the somatostatin sst2 receptor. The fate of internalized agonists and receptors is of critical importance because the rate of ligand recycling back to the cell surface can limit the amount of radioligand accumulated inside the cells, whereas receptor recycling might be of vital importance in providing the cell surface with deph...

Somatostatin receptors subtypes (SSTR 1-5) were demonstrated in surgically obtained adrenal gland tumors by means of immunohistochemistry (IHC). Results of the present study demonstrate that somatostatin receptors are expressed in adrenal tumors in a varied manner which is specific in each case. It provides different diagnostic and therapeutic possibilities.