Effects of phorbol esters on excitation-contraction coupling and protein kinase C activity of frog twitch muscle fibers

1999 ◽  
Vol 438 (1) ◽  
pp. 61-67 ◽  
Author(s):  
X. H. Zhang ◽  
J. H. Sun ◽  
P. H. Zhu
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Muscle Fibers ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Kinase C ◽  
Protein Kinase C Activity

Autoregulation of muscarinic and gastrin receptors on gastric parietal cells

1989 ◽  
Vol 256 (2) ◽  
pp. G356-G363 ◽  
Author(s):  
T. Chiba ◽  
S. K. Fisher ◽  
B. W. Agranoff ◽  
T. Yamada
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Parietal Cell ◽  
Phorbol Esters ◽  
Cell Function ◽  
Inhibitory Effect ◽  
Parietal Cells ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Inositol Phospholipids

In previous studies we demonstrated that parietal cell stimulation with gastrin and carbamoylcholine (carbachol) is accompanied by increased turnover of membrane inositol phospholipids. We conducted the present studies to examine whether membrane-associated protein kinase C activity is enhanced as a consequence of these events and to explore the role of this enzyme in regulating parietal cell function. We observed that carbachol and gastrin dose dependently increased membrane-associated protein kinase C activity while histamine did not. Furthermore, compounds such as phorbol esters and diacylglycerol, which are known to be direct stimulants of protein kinase C activity, also stimulated parietal cell aminopyrine uptake. In contrast, the phorbol ester 12-O-tetradecanoylphorbol-13-acetate and the synthetic diacylglycerol 1-oleoyl-2-acetyl-sn-glycerol inhibited both aminopyrine uptake and membrane inositol phospholipid turnover in parietal cells induced by carbachol and gastrin. The inhibitory effect appeared to result from reduction in the quantity of muscarinic and gastrin receptors without alterations in their specific affinities. These data suggest that protein kinase C mediates stimulation of parietal cells by gastrin and carbachol but also activates an autoregulatory mechanism via downregulation of muscarinic and gastrin receptors.

scholarly journals Involvement of calcium-sensitive phospholipid-dependent protein kinase in control of acid secretion by isolated rat parietal cells

1985 ◽  
Vol 232 (2) ◽  
pp. 609-611 ◽  
Author(s):  
N G Anderson ◽  
P J Hanson
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Acid Secretion ◽  
Phorbol Esters ◽  
Inhibitory Effect ◽  
Dependent Protein Kinase ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Dependent Protein ◽  
Isolated Rat

The relative potency with which phorbol esters inhibited histamine-stimulated aminopyrine accumulation (an index of acid secretion) paralleled that which has been established for the activation of purified protein kinase C. The inhibitory effect of 1-oleoyl-2-acetylglycerol on aminopyrine accumulation stimulated by various secretagogues was similar to that of 12-O-tetradecanoylphorbol 13-acetate. Protein kinase C activity was present in a parietal-cell-enriched fraction. In conclusion, protein kinase C could be involved in mechanisms regulating gastric acid secretion.

scholarly journals Comparison of effects of phorbol esters and glucose on protein kinase C activation and insulin secretion in pancreatic islets

1989 ◽  
Vol 264 (1) ◽  
pp. 27-33 ◽  
Author(s):  
R A Easom ◽  
J H Hughes ◽  
M Landt ◽  
B A Wolf ◽  
J Turk ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Pancreatic Islets ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Protein Kinase Activity ◽  
Isolated Pancreatic Islets ◽  
Kinase C ◽  
Protein Kinase C Activity

The tumour-promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) induces insulin secretion from isolated pancreatic islets, and this suggests a potential role for protein kinase C in the regulation of stimulus-secretion coupling in islets. In the present study, the hypothesis that the insulinotropic effect of TPA is mediated by activation of protein kinase C in pancreatic islets has been examined. TPA induced a gradual translocation of protein kinase C from the cytosol to a membrane-associated state which correlated with the gradual onset of insulin secretion. The pharmacologically inactive phorbol ester 4 alpha-phorbol 12,13-didecanoate did not mimic this effect. TPA also induced a rapid time-dependent decline of total protein kinase C activity in islets and the appearance of a Ca2+- and phospholipid-independent protein kinase activity. Insulin secretion induced by TPA was completely suppressed (IC50 approximately 10 nM) by staurosporine, a potent protein kinase C inhibitor. Staurosporine also inhibited islet cytosolic protein kinase C activity at similar concentrations (IC50 approximately 2 nM). In addition, staurosporine partially (approximately 60%) inhibited glucose-induced insulin secretion at concentrations (IC50 approximately 10 nM) similar to those required to inhibit TPA-induced insulin secretion, suggesting that staurosporine may act at a step common to both mechanisms, possibly the activation of protein kinase C. However, stimulatory concentrations of glucose did not induce down-regulation of translocation of protein kinase C, and the inhibition of glucose-induced insulin release by staurosporine was incomplete. Significant questions therefore remain unresolved as to the possible involvement of protein kinase C in glucose-induced insulin secretion.

Phorbol esters, protein kinase C, and thyroxine 5'-deiodinase in brown adipocytes

1988 ◽  
Vol 254 (3) ◽  
pp. E323-E327 ◽  
Author(s):  
R. M. Barge ◽  
I. Mills ◽  
J. E. Silva ◽  
P. R. Larsen
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Particulate Fraction ◽  
Brown Adipocyte ◽  
Adrenergic Agonists ◽  
Brown Adipocytes ◽  
Kinase C ◽  
Deiodinase Activity ◽  
Protein Kinase C Activity

Protein kinase C activity has been identified in the rat brown adipocyte. About 60% of this activity is found in the cytosolic fraction under basal conditions, and 12-O-tetradecanoylphorbol 13-acetate (TPA) causes a rapid shift from the cytosol to the particulate fraction. Norepinephrine and phenylephrine cause a similar redistribution that can be blocked by prazosin but not by alprenolol. alpha 1-Adrenergic agonists cause three- to fivefold stimulation of type 2 iodothyronine 5'-deiodinase activity in brown adipocytes. TPA has no effect on basal deiodinase activity and reduces the response of the enzyme to alpha 1-adrenergic agonists. These results suggest that the translocation of protein kinase C from cytosol to particulate fraction is not sufficient to increase deiodinase activity but can modulate the alpha 1-adrenergic agonist-mediated responses in these cells.

Activation of protein kinase C inhibits synthesis and release of decidual prolactin

1986 ◽  
Vol 251 (2) ◽  
pp. E172-E177
Author(s):  
I. Harman ◽  
A. Costello ◽  
B. Ganong ◽  
R. M. Bell ◽  
S. Handwerger
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Dependent Manner ◽  
Prolactin Release ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Decidual Cells ◽  
Prolactin Synthesis ◽  
Activate Protein Kinase

Activation of calcium-activated, phospholipid-dependent protein kinase C by diacylglycerol and phorbol esters has been shown to mediate release of hormones in many systems. To determine whether protein kinase C activation is also involved in the regulation of prolactin release from human decidua, we have examined the effects of various acylglycerols and phorbol esters on the synthesis and release of prolactin from cultured human decidual cells. sn-1,2-Dioctanoylglycerol (diC8), which is known to stimulate protein kinase C in other systems, inhibited prolactin release in a dose-dependent manner with maximal inhibition of 53.1% (P less than 0.01) at 100 microM. Diolein (100 microM), which also stimulates protein kinase C activity in some systems, inhibited prolactin release by 21.3% (P less than 0.05). Distearin and dipalmitin, which are much less effective in activating protein kinase C, and monopalmitin and tripalmitin, which do not activate protein kinase C, had no significant effect on prolactin release. Phorbol 12-myristate 13-acetate (PMA), phorbol 12,13-didecanoate, and 4 beta-phorbol 12,13-dibutyrate, which activate protein kinase C in other systems, also inhibited the release of prolactin, while the protein kinase C inactivate 4 alpha-phorbol-12,13-didecanoate was without effect. The inhibition of prolactin release was secondary to a decrease in prolactin synthesis. The amounts of prolactin synthesized by cells exposed to diC8 (300 microM) or PMA (10(-7) M) for 30 min were 56.3 and 50.0% less than that synthesized by control cells (P less than 0.01 in each instance).(ABSTRACT TRUNCATED AT 250 WORDS)

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