The Effect of Cadmium on Cytosolic Free Calcium, Protein Kinase C, and Collagen Synthesis in Rat Osteosarcoma (ROS 17/2.8) Cells

1997 ◽  
Vol 143 (1) ◽  
pp. 189-195 ◽  
Author(s):  
Gregory J. Long
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Collagen Synthesis ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Kinase C

scholarly journals Inositol lipid metabolism and signal transduction in clonal pituitary cells

1986 ◽  
Vol 124 (1) ◽  
pp. 337-358
Author(s):  
A. H. Drummond
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Prolactin Secretion ◽  
Free Calcium ◽  
Pituitary Cells ◽  
Cytosolic Free Calcium ◽  
Release Process ◽  
Cell Functions ◽  
Kinase C ◽  
Inositol 1,4,5 Trisphosphate

A number of clonal cell lines derived from a rat pituitary tumour, collectively termed GH cells, have retained a range of differentiated cell functions, including their ability to secrete the hormones prolactin and growth hormone in response to stimuli such as thyrotropin-releasing hormone (TRH). The mechanisms underlying this release process involve, at least in part, an increase in cytosolic free calcium levels, and the cells have proved useful as a model system in studies of receptor-controlled calcium mobilization. The initial response of the cells to the addition of TRH now appears to be the interaction of the occupied TRH receptor with a GTP-binding protein. A sophisticated signalling system is then activated which initially involves the phosphodiesteratic hydrolysis of phosphatidylinositol 4,5-bisphosphate to 1,2-diacylglycerol and inositol 1,4,5-trisphosphate. Both of these products are important intracellular messengers, and their formation leads to a plethora of biochemical and electrical changes which culminate in the biphasic release of hormone from the cell. The changes in cytosolic free calcium that occur following TRH addition follow a complex temporal pattern. Within 1 s, the concentration starts to increase from a resting level, in the range 100–150 nmol l-1, to a peak value of around 1 mumol l-1 which is attained within 6–8 s. This ‘spike’ of calcium is almost exclusively derived from intracellular stores, probably the endoplasmic reticulum, in response to the formation of inositol 1,4,5-trisphosphate. With high concentrations of the peptide, the cytosolic free calcium concentration declines promptly, due to the activation of a protein kinase C-mediated extrusion and/or sequestration process. This inhibitory phase is less marked at low agonist concentrations but, in all cases, is superseded by a second increase in free calcium, which is due to the stimulated influx of the cation through dihydropyridine-sensitive calcium channels. These biphasic changes in calcium, in concert with the activation of protein kinase C, appear sufficient to regulate prolactin secretion.

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