Gonadal steroid effects on LH response to arachidonic acid and protein kinase C

1988 ◽  
Vol 255 (3) ◽  
pp. E314-E321
Author(s):  
F. Kamel ◽  
C. L. Kubajak
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Luteinizing Hormone ◽  
Pituitary Cells ◽  
Gonadal Steroid ◽  
Kinase C ◽  
Rat Pituitary Cells ◽  
Lh Secretion ◽  
Pkc Activation

Cultured rat pituitary cells were used to examine, first, the effects of luteinizing hormone-releasing hormone, Ca2+ mobilization, protein kinase C (PKC) activation, and arachidonic acid (AA) on luteinizing hormone (LH) secretion and AA release, and, second, gonadal steroid modulation of these effects. A23187, 12-O-tetradecanoylphorbol 13-acetate (TPA), and AA stimulated LH secretion by both perifused and static cultures; TPA facilitated the responses to both A23187 and AA. LHRH, A23187, and TPA stimulated AA release. Inhibition of AA metabolism reduced the LH responses to LHRH, A23187, TPA, and melittin. Pretreatment with testosterone inhibited the LH response to LHRH but not the responses to TPA or AA. Pretreatment with 17 beta-estradiol stimulated the LH responses to LHRH, TPA, and low concentrations of AA. These results suggest that LHRH action involves a cascade of events, in which the effects of Ca2+ mobilization and PKC activation are mediated at least in part by AA release. They further suggest that both testosterone and 17 beta-estradiol modulate LH secretion by affecting AA release; 17 beta-estradiol may also affect some process subsequent to AA release.

scholarly journals Requirement for diacylglycerol and protein kinase C in HeLa cell-substratum adhesion and their feedback amplification of arachidonic acid production for optimum cell spreading.

1993 ◽  
Vol 4 (3) ◽  
pp. 271-281 ◽  
Author(s):  
J S Chun ◽  
B S Jacobson
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Hela Cell ◽  
Cell Attachment ◽  
Cell Spreading ◽  
Subsequent Formation ◽  
Sequence Of Events ◽  
Kinase C ◽  
Pkc Activation

Release of arachidonic acid (AA) and subsequent formation of a lipoxygenase (LOX) metabolite(s) is an obligatory signal to induce spreading of HeLa cells on a gelatin substratum (Chun and Jacobson, 1992). This study characterizes signaling pathways that follow the LOX metabolite(s) formation. Levels of diacylglycerol (DG) increase upon attachment and before cell spreading on a gelatin substratum. DG production and cell spreading are insignificant when phospholipase A2 (PLA2) or LOX is blocked. In contrast, when cells in suspension where PLA2 activity is not stimulated are treated with exogenous AA, DG production is turned on, and inhibition of LOX turns it off. This indicates that the formation of a LOX metabolite(s) from AA released during cell attachment induces the production of DG. Consistent with the DG production is the activation of protein kinase C (PKC) which, as with AA and DG, occurs upon attachment and before cell spreading. Inhibition of AA release and subsequent DG production blocks both PKC activation and cell spreading. Cell spreading is also blocked by the inhibition of PKC with calphostin C or sphingosine. The inhibition of cell spreading induced by blocking AA release is reversed by the direct activation of PKC with phorbol ester. However, the inhibition of cell spreading induced by PKC inhibition is not reversed by exogenously applied AA. In addition, inhibition of PKC does not block AA release and DG production. The data indicate that there is a sequence of events triggered by HeLa cell attachment to a gelatin substratum that leads to the initiation of cell spreading: AA release, a LOX metabolite(s) formation, DG production, and PKC activation. The data also provide evidence indicating that HeLa cell spreading is a cyclic feedback amplification process centered on the production of AA, which is the first messenger produced in the sequence of messengers initiating cell spreading. Both DG and PKC activity that are increased during HeLa cell attachment to a gelatin substratum appear to be involved. DG not only activates PKC, which is essential for cell spreading, but is also hydrolyzed to AA. PKC, which is initially activated as consequence of AA production, also increases more AA production by activating PLA2.

Arachidonic acid-induced LH release is ATP-independent and insensitive to N-ethyl maleimide

1992 ◽  
Vol 132 (1) ◽  
pp. 77-82 ◽  
Author(s):  
P. V. Kaye ◽  
P. A. van der Merwe ◽  
R. P. Millar ◽  
J. S. Davidson
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Pituitary Cells ◽  
Cell Permeabilization ◽  
Intact Cells ◽  
Permeabilized Cells ◽  
Kinase C ◽  
Lh Release ◽  
Stimulation Of

ABSTRACT The mechanism of arachidonic acid (AA)-induced LH release was characterized using sheep pituitary cells in primary culture permeabilized with Staphylococcal α-toxin. In intact cells, exogenous AA evoked release of LH in a manner which was partially dependent on extracellular Ca2+. At similar concentrations, AA also caused cell permeabilization as monitored by efflux of [3H]2-deoxyglucose metabolites. In α-toxin-permeabilized cells where cytosolic Ca2+ was clamped at resting levels, AA retained its ability to cause LH release. Unlike the stimulation of exocytosis produced by Ca2+, phorbol ester or cyclic AMP, AA-evoked release was independent of ATP and was not inhibited by pretreatment with N-ethyl maleimide. These findings indicated that exogenous AA does not cause LH release by Ca2+ influx or mobilization or by activating protein kinase C. The results suggest that LH release induced by exogenous AA is probably due to its detergent-like properties, and does not represent true exocytosis. Journal of Endocrinology (1992) 132, 77–82

Phospholipase activation and secretion: evidence that PLA2, PLC, and PLD are not essential to exocytosis

1996 ◽  
Vol 270 (4) ◽  
pp. C1153-C1163 ◽  
Author(s):  
J. R. Coorssen
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phosphatidic Acid ◽  
Phospholipase D ◽  
Human Platelets ◽  
Pla2 Activity ◽  
Kinase C ◽  
Gamma S ◽  
Pkc Activation

Numerous studies have identified phospholipase metabolites as membrane fusogens, and phospholipase D (PLD) (J.R. Coorssen and R.J. Haslam. FEBS Lett. 316: 170-174, 1993), C (PLC), and A2 (PLA2) activities correlate with secretion. Do these enzymes have essential or modulatory roles? This study confirms that secretion does not require Ca2+ or PLC (Coorssen et al. Cell Regul. 1: 1027-1041, 1990). Arachidonic acid (AA), phosphatidic acid (PA) and analogues, exogenous metabolites of PLA2 and PLD, were tested in electropermeabilized human platelets. AA potentiated guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)-induced secretion, and eicosanoids were not essential. Endogenous [3H]AA formation correlated with GTP gamma S-induced secretion, and phorbol 12-myristate 13-acetate (PMA) promoted these effects. Inhibitors were used to probe phospholipase influences on secretion. Only PLD inhibitors blocked secretion. However, PMA blocked inhibition of protein kinase C (PKC) and secretion by quercetin, suggesting that PA formed by PLD supports PKC activation and GTP gamma S-induced secretion. Thus PA analogues had no effect alone but enhanced GTP gamma S-induced PKC activity and secretion. Slower PLD activation compared with secretion also indicates a nonessential role. This is the first report of a Ca(2+)-independent PLA2 activity in human platelets, use of quercetin as a PLD inhibitor, and dissociation of PLA2, PLC, and PLD activities from secretion. No major phospholipase activities are essential to the final steps in exocytosis, but modulatory roles are indicated.

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