Evidence that somatostatin is localized and synthesized in lymphoid organs.

Abstract

Because several peptides ornally found in the pituitary as within the central nervous system have been l i in lymphoid tissues and because somatostatin (soma inrelease-inhibiting hormone, SRIH) can act on cells ofthe immune system, we searched for this peptide in lymphoid organs. We demonstrated that SRIH mRNA exists in lymphoid tissue, albeit in smaller levels than in the perive region of the hypotaus, the brain region that contains the highest level of this mRNA. SRIH mRNA was found in the spleen and thymus ofmale rats and in the spleen, thymus, and bursa of Fabricius of the chicken. Its loc ton in the bursa indices that the peptide must be present in B lymphocytes since this is the site of origin of B lymphocytes in birds. The SRII concentration in these lymphoid organs as determined by radloimmunoassay was greater in the thymus than in the spleen of the rat. These concentrations were 50 times less than those found in the periventricular region of the hypodtalmus, the site ofthe perikarya ofSRIH-containing neurons. In the chicken, as in the rat, the concentration of SRII was greater in the thymus than in the spleen; it was present in the bursa ofFabridus, also in higher concentration than in the spleen.Fluorescence immucytochemir revealed the presence of SRIH-positive cells in dusters inside the white pulp and more dispersed within the red pulp ofthe spleen of both the rat and the chicken. The thymus from these species o contained SRIHpositive cells within the medulla and around the ctcomedullary junction. In the chicken, there were large'dusters of SRIHpositive cells in the medullary portion ofeach nodule of the bursa ofFabricius. Preabsorptionoftheprimayantiseru orreplacing this antiserum with normal rabbit serum verified the specificity of aning. Sequential immunostainingof the same sections from rat spleen using first SRIH antibody and subsequently a monoclonal antibody against a rat B-cell surface antigen revealed the presence of SRIH immunoreactivity in some, but not all, B cells. Other cell types in spleen not yet identified also stained positively with the SR.II antibody but were not reactive to monoclonal antibodies to rat Thy-1.1, a marker for all the thymic T lymphocytes. The possibility that SRIH is present in other populations ofcells in the spleen cannot be ruled out. Sequential immu nin of the same sections of rat thymus revealed the presence of SRIH immunoreactivity in a small population of T lymphocytes in the medulla, as revealed by the Thy-1.1 marker. The SRIH-positive cells were nonimmunoreactive when exposed tothe B-cell marker; however, the possibility that SRIH is present in other cells was not investigated. Thus, our results indicate that SRIH is synthesized and stored in cells of the immune system. SRHI may be secreted from these cells to exert paracine actions that alter the function of immune cells in spleen and thymus.Somatostatin (somatotropin-release-inhibiting hormone, SRIH), originally described and isolated from the hypothalamus (1, 2) by its ability to inhibit growth ...

Induction of a negative autocrine loop by expression of sst2 somatostatin receptor in NIH 3T3 cells.

“…Indeed, a variety of normal cells, including endocrine and lymphoid cells, that synthesize endogenous somatostatin are known to express somatostatin receptors (28)(29)(30). Furthermore, immunoreactive somatostatin has been found in various types of somatostatin receptor-positive tumor cell lines such as breast cancer cells and colonic tumor cells (31,32) and somatostatin mRNA was detected in a wide variety of neuroendocrine tumors known to express somatostatin receptors (33,34).…”

“…First-strand cDNA synthesis was then carried out with total RNA in 50 mM Tris-HCl buffer (pH 8.3) containing 200 U of Moloney murine leukemia virus reverse transcriptase, 26.5 M oligod(T), 1 mM dNTP, 20 U RNAsin, 10 mM dithiothreitol, 75 mM KCl, 3 mM MgCl 2 in a final volume of 20 l. The sample was incubated for 10 min at 23 Њ C followed by 2 h at 39 Њ C. The RT mixture was then chilled on ice and diluted two-fold with sterile water. PCRs were carried out as described (36) with 1.25 U of Taq polymerase, 1 M specific sense and antisense primers, 250 M of dNTPs, in 10 mM Tris-HCl buffer (pH 9) containing 50 mM KCl, 1.5 mM MgCl 2 , 0.01% Triton X-100 in a final volume of 50 l. After denaturation of the sample at 94 Њ C for 10 min, PCR was carried out on a DNA Thermal Cycler (Techné Laboratories, Princeton) for varying sequential (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) cycles with denaturation at 94 Њ C for 1 min, annealling at 51-62 Њ C for 1 min, and extension at 72 Њ C for 1.5 min. The amplification was terminated by a final extension step at 72 Њ C for 10 min.…”

Physiological and pathophysiological role of somatostatin receptors in the human thymus

“…Among lymphatic organs, the thymus from different species, including the human, has been shown to contain the highest amount of SS (7,8,18). Although experimental models in animals have suggested the signi®cant participation of different neuropeptides in the activities of the thymus, the exact role of SS in this context is still obscure.…”

Tissue Distribution of Ca2+-dependent Activator Protein for Secretion Family Members CAPS1 and CAPS2 in Mice

“…Previous studies reported the expressions of neurotrophin-3 (KatohSemba et al 1996), brain-derived neutrotrophic factor (Katoh-Semba et al 1997), vasoactive intestinal peptide (Gomariz et al 1993), and somatostatin (Aguila et al 1991) in minor cell types of these two tissues. Expression of methionine-enkephalin, neuropeptide Y, and substance P were also reported in a similar cell subset of the thymus (Atoji et al 1997).…”