scholarly journals Rapid increases in inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and cytosolic free Ca2+ in agonist-stimulated pancreatic acini of the rat. Effect of carbachol, caerulein and secretin

1987 ◽  
Vol 242 (1) ◽  
pp. 289-292 ◽  
Author(s):  
E R Trimble ◽  
R Bruzzone ◽  
C J Meehan ◽  
T J Biden
Keyword(s):  
Time Course ◽  
Inositol Trisphosphate ◽  
Second Messenger ◽  
Pancreatic Acini ◽  
Inositol 1,4,5 Trisphosphate ◽  
Rapid Formation ◽  
Initial Elevation

We compared the time course of increases in isomers of inositol trisphosphate [Ins(1,4,5)P3] and Ins(1,3,4)P3] and the tetrakisphosphate [Ins(1,3,4,5)P4] with changes in cytosolic free Ca2+ [(Ca2+]i) in dispersed pancreatic acini of the rat. There were rapid (5s) increases in Ins(1,4,5)P3 and Ins(1,3,4,5)P4 in response to carbachol, caerulein and secretin, whereas Ins(1,3,4)P3 increased more slowly. All three secretagogues induced increases in [Ca2+]i, which reached a peak at 15-20 s. Our results indicate that the very rapid formation of Ins(1,4,5)P3 is compatible with its second-messenger role in the initial elevation of [Ca2+]i.

scholarly journals Calcium modulates the generation of inositol 1,3,4-trisphosphate in human platelets by the activation of inositol 1,4,5-trisphosphate 3-kinase

1988 ◽  
Vol 253 (3) ◽  
pp. 789-794 ◽  
Author(s):  
J L Daniel ◽  
C A Dangelmaier ◽  
J B Smith
Keyword(s):  
Phospholipase C ◽  
Inositol Trisphosphate ◽  
Second Messenger ◽  
Dienoic Acid ◽  
Human Platelets ◽  
Inositol 1,4,5 Trisphosphate

We observed that more total inositol trisphosphate (InsP3) was formed when human platelets were stimulated with agonists (15-hydroxy-9,11-azo-prosta-5,13-dienoic acid or thrombin) in the presence of extracellular Ca2+ than in its absence. Analysis of the InsP3 by h.p.l.c. indicated that the increased InsP3 formed in the presence of extracellular Ca2+ was primarily the 1,3,4-trisphosphate [Ins(1,3,4)P3]. In addition, more inositol 1,3,4,5-tetrakisphosphate (InsP4) was formed in the presence of extracellular Ca2+. Experiments conducted with electrically permeabilized platelets demonstrated that conversion of [3H]Ins(1,4,5)P3 to [3H]InsP4 in platelets was Ca2+-dependent, with half-maximal conversion observed at approx. 2.5 microM-Ca2+. By contrast, dephosphorylation of [3H]InsP4 to [3H]Ins(1,3,4)P3 was not activated by Ca2+. A partially purified preparation of Ins(1,4,5)P3 3-kinase from human platelets was found to be insensitive to Ca2+, but addition of calmodulin restored Ca2+-sensitivity to the kinase, increasing its activity about 5-fold. These results show that in human platelets the metabolism of Ins(1,4,5)P3 is regulated by Ca2+-calmodulin, and suggest that the metabolites of Ins(1,4,5)P3 may also have important second-messenger functions in platelets, and are consistent with the hypothesis that the activation of phospholipase C is not dependent on extracellular Ca2+.

Rapid formation of inositol 1,4,5-trisphosphate in rat pancreatic acini stimulated by carbamylcholine

1987 ◽  
Vol 928 (3) ◽  
pp. 341-348 ◽  
Author(s):  
Claire Doughney ◽  
Graham R. Brown ◽  
Margaret A. McPherson ◽  
Robert L. Dormer
Keyword(s):  
Pancreatic Acini ◽  
Inositol 1,4,5 Trisphosphate ◽  
Rapid Formation

Selective permeability of different connexin channels to the second messenger inositol 1,4,5-trisphosphate

2000 ◽  
Vol 113 (8) ◽  
pp. 1365-1372 ◽  
Author(s):  
H. Niessen ◽  
H. Harz ◽  
P. Bedner ◽  
K. Kramer ◽  
K. Willecke
Keyword(s):  
Gap Junctions ◽  
Hela Cells ◽  
Second Messenger ◽  
Pancreatic Acinar Cells ◽  
Cell Coupling ◽  
Liver Parenchymal ◽  
Fura 2 ◽  
Inositol 1,4,5 Trisphosphate ◽  
Messenger Molecules ◽  
Parenchymal Cells

Intercellular propagation of signals through connexin32-containing gap junctions is of major importance in physiological processes like nerve activity-dependent glucose mobilization in liver parenchymal cells and enzyme secretion from pancreatic acinar cells. In these cells, as in other organs, more than one type of connexin is expressed. We hypothesized that different permeabilities towards second messenger molecules could be one of the reasons for connexin diversity. In order to investigate this, we analyzed transmission of inositol 1,4,5-trisphosphate-mediated calcium waves in FURA-2-loaded monolayers of human HeLa cells expressing murine connexin26, -32 or -43. Gap junction-mediated cell coupling in different connexin-transfected HeLa cells was standardized by measuring the spreading of microinjected Mn(2+) that led to local quenching of FURA-2 fluorescence. Microinjection of inositol 1,4,5-trisphosphate into confluently growing HeLa connexin32 transfectants induced propagation of a Ca(2+) wave from the injected cell to neighboring cells that was at least three- to fourfold more efficient than in HeLa Cx26 cells and about 2.5-fold more efficient than in HeLa Cx43 transfectants. Our results support the notion that diffusion of inositol 1,4,5-trisphosphate through connexin32-containing gap junctions is essential for the optimal physiological response, for example by recruiting liver parenchymal cells that contain subthreshold levels of this short lived second messenger.

Inositol-1,4,5-trisphosphate injection mimics fertilization potentials in sea urchin eggs

1986 ◽  
Vol 250 (2) ◽  
pp. C340-C344 ◽  
Author(s):  
B. E. Slack ◽  
J. E. Bell ◽  
D. J. Benos
Keyword(s):  
Membrane Potential ◽  
Partial Response ◽  
Sea Urchin ◽  
Time Course ◽  
Strongylocentrotus Purpuratus ◽  
Sea Urchin Eggs ◽  
Low Calcium ◽  
Inositol 1,4,5 Trisphosphate

The effects of inositol-1,4,5-trisphosphate (IP3) and of diacylglycerol (DAG) and its analogues on the membrane potential of eggs from the sea urchin Strongylocentrotus purpuratus were examined. Injection of IP3 into eggs resulted in a change in membrane potential that was similar in magnitude and time course to the fertilization potential elicited by sperm attachment. In low-calcium seawater, IP3 injection elicited a partial response. DAG and its analogues phorbol myristyl acetate and 1-oleoyl-2-acetylglycerol did not affect membrane potential either when applied by perfusion or when injected. The results indicate that IP3, but not DAG or its analogues, may be involved in the generation of the fertilization potential triggered by the interaction of sperm with sea urchin eggs.

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