Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polyphosphates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed1988

PTH elevates inositol polyphosphates and diacylglycerol in a rat osteoblast-like cell line.

Parathyroid hormone (PTH)-stimulated signal transduction through mechanisms alternate to adenosine 3',5'-cyclic monophosphate (cAMP) production were studied in UMR 106-01 cells, a cell line with an osteoblastic phenotype. PTH produced transient, dose-related increases in cytosolic calcium [( Ca2+]i), inositol trisphosphates, and diacylglycerol (DAG). Both inositol 1,4,5-trisphosphate (Ins-1,4,5P3) and inositol 1,3,4-trisphosphate (Ins-1,3,4P3) production were rapidly stimulated by PTH. Consistent with the production of Ins-1,3,4P3, rapid stimulation of late eluting inositol tetrakisphosphate was observed. The effects on the inositol phosphates were induced rapidly, consistent with roles as signals for changes in [Ca2+]i. In saponin-permeabilized UMR 106-01 cells, Ins-1,4,5P3 stimulated 45Ca release from a nonmitochondrial intracellular pool. Thus the hypothesis that PTH-stimulated Ins-1,4,5P3 production initiates Ca2+ release and contributes to transient elevations of [Ca2+]i is supported. Pretreatment of UMR 106-01 cells with pertussis toxin had no effect on PTH stimulation of inositol phosphates. Pertussis toxin reduced PTH-stimulated elevations of [Ca2+]i, but cAMP analogues had an even greater effect than pertussis toxin. These data suggest that stimulation of cAMP production during PTH stimulation may negatively affect production of rises in [Ca2+]i during PTH stimulation. The inactivation of the inhibitory G protein of adenylate cyclase by pertussis toxin could explain its action similar to cAMP analogues. Cyclic nucleotides diminish the effects of PTH on [Ca2+]i, probably interacting on a biochemical step subsequent to or independent of Ins-1,4,5P3 release.

Adenylate Cyclase Toxin↗
PubMed1992

Time course of thrombin-induced increase in endothelial permeability: relationship to Ca2+i and inositol polyphosphates.

The temporal relationship between the alpha-thrombin-induced increase in transendothelial permeability and the alpha-thrombin-mediated changes in several key transmembrane signaling events was examined in confluent monolayers of bovine pulmonary artery endothelial cells (BPAEC). The time courses of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] generation, changes in cytosolic [Ca2+] ([Ca2+]i), and reorganization of cytoskeletal F-actin were determined to assess the relationship between these events and the onset of the alpha-thrombin-induced increase in endothelial permeability. alpha-Thrombin (10(-7) M) increased the transendothelial 125I-albumin clearance rate half-maximally by approximately 1 min and maximally by approximately 2 min (160% over control level). The increase in permeability occurred concomitantly with reorganization of F-actin cytoskeleton (i.e., loss of peripheral band and increased stress fiber density) and increased actin polymerization. Stimulation of fura-2-loaded BPAEC with 10(-7) M alpha-thrombin produced a typical biphasic rise in [Ca2+]i. The initial rapid increase in [Ca2+]i peaked by approximately 16 s after thrombin challenge and the [Ca2+]i response showed a slow decrease to half-maximal within 50 s. The alpha-thrombin-induced increase in permeability as well as the increase in [Ca2+]i were consistently preceded by increased Ins(1,4,5)P3 generation detectable within 10 s after thrombin challenge. These results indicate that alpha-thrombin triggers a cascade of events (i.e., Ins(1,4,5)P3 generation and the ensuing rise in [Ca2+]i), which may comprise the second messengers that mediate F-actin reorganization and the increase in endothelial permeability.

Actins↗
PubMed1989

Inositol tris- and polyphosphate formation during chemotaxis of Dictyostelium.

Using the technique of HPLC with Partisil SAX columns, we have found that stimulation of amoebae of Dictyostelium discoideum with the chemoattractant cyclic AMP induces the rapid accumulation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), with a peak at 5 s. A smaller HPLC peak (designated P3) that elutes just after the Ins(1,4,5)P3 peak accumulates more slowly to a maximum at 20 s. In control studies, the changes in Ins(1,4,5)P3 were shown not to be due to varying recovery from the cell extracts and a comparison of reverse-phase and Partisil SAX HPLC columns showed similar values for determinations by either method. The involvement of a G-protein in this chemotactic system was confirmed by the finding that accumulation of Ins(1,4,5)P3 was elicited by the addition of GTP gamma S (5'-[gamma-thio]triphosphate) to saponin-permeabilized amoebae. A study of the changes in the lipid-soluble phosphatidyl inositol phosphates demonstrated that cyclic AMP also stimulated a rapid loss of radioactivity from 32P-labelled phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), which corresponded in its timing to the rise in Ins(1,4,5)P3, indicating that a phosphoinositidase C (phospholipase C) is present that can be stimulated by occupation of the cell surface cyclic AMP receptors.

Animals↗