Oxytocin induced a biphasic increase in the intracellular Ca2+ concentration of porcine myometrial cells: Participation of a pertussis toxin?insensitive G-protein, inositol 1,4,5-trisphosphate?sensitive Ca2+ pool, and Ca2+ channels

1995 ◽  
Vol 41 (1) ◽  
pp. 20-28 ◽  
Author(s):  
Ronghua Zhuge ◽  
Siben Li ◽  
Ter-Hsin Chen ◽  
Walter H. Hsu
Keyword(s):  
G Protein ◽  
Pertussis Toxin ◽  
Myometrial Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Ca2 Channels

Pancreatic polypeptide inhibits calcium channels in rat sympathetic neurons via two signaling pathways

1995 ◽  
Vol 73 (3) ◽  
pp. 1323-1328 ◽  
Author(s):  
L. P. Wollmuth ◽  
M. S. Shapiro ◽  
B. Hille
Keyword(s):  
G Protein ◽  
Pertussis Toxin ◽  
Pancreatic Polypeptide ◽  
Sympathetic Neurons ◽  
Whole Cell ◽  
Adult Rat ◽  
Voltage Dependent ◽  
Cervical Ganglion ◽  
Gamma S ◽  
Ca2 Channels

1. We studied modulation of N-type Ca2+ channels in adult rat superior cervical ganglion (SCG) neurons by pancreatic polypeptide (PP) using whole cell clamp. In large (> 20 pF) SCG neurons, PP inhibited ICa (35 +/- 2%, mean +/- SE) in a concentration-dependent fashion, with one-half maximal inhibition at 19 nM. 2. One-third of the inhibition was blocked by pertussis toxin, about one-half was blocked by N-ethylmaleimide (NEM) treatments, and about one-half was voltage dependent. The NEM-insensitive component of the PP inhibition was voltage independent and not significantly blocked by intracellular Ca2+ chelators. 3. The NEM-insensitive component was only weakly attenuated by GDP-beta-S, and moderately reversible with guanosine 5'-triphosphate (GTP)-gamma-S, in the whole cell pipette, leaving open the possibility that it is not mediated by a G protein. 4. Hence, PP inhibits ICa via two mechanisms: one G-protein-mediated and the other possibly G-protein independent. The former pathway is sensitive to pertussis toxin (PTX) and NEM, voltage dependent, and shared by several other transmitters in these cells. The latter pathway is PTX-and NEM-insensitive, not voltage dependent, and not affected by the presence of intracellular Ca2+ chelators.

scholarly journals Role of pertussis toxin-sensitive G-protein, K+ channels, and voltage-gated Ca2+ channels in the antinociceptive effect of inosine

2012 ◽  
Vol 9 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Sérgio José Macedo-Junior ◽  
Francisney Pinto Nascimento ◽  
Murilo Luiz-Cerutti ◽  
Adair Roberto Soares Santos
Keyword(s):  
G Protein ◽  
Pertussis Toxin ◽  
Antinociceptive Effect ◽  
K Channels ◽  
Voltage Gated ◽  
Ca2 Channels

Oxytocin-stimulated phosphoinositide hydrolysis in human myometrial cells: involvement of pertussis toxin-sensitive and -insensitive G-proteins

1993 ◽  
Vol 136 (3) ◽  
pp. 497-NP ◽  
Author(s):  
S. Phaneuf ◽  
G. N. Europe-Finner ◽  
M. Varney ◽  
I. Z. MacKenzie ◽  
S. P. Watson ◽  
...  
Keyword(s):  
G Protein ◽  
Pertussis Toxin ◽  
Inositol Phosphates ◽  
Phosphoinositide Hydrolysis ◽  
Maximal Response ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Myometrial Cells ◽  
Uterine Contractions

ABSTRACT Phosphoinositide hydrolysis is important in mediating the actions of oxytocin and prostaglandin (PG) F2α on uterine contractions during labour. We have measured the effect of oxytocin, PGF2α and other agents on the formation of inositol phosphates (IPs) in cultured human myometrial cells labelled with [3H]inositol and on changes in intracellular free Ca2+ concentration ([Ca2 + ]i) in cells loaded with Fura-2. Oxytocin induced the formation of [3H]IPs in a concentration-dependent manner with an EC50 (concentration of agonist producing 50% of the maximal response) of 1·4 ±0·5 nmol/l (mean ± s.e.m.). The maximal response was obtained with 1 μmol oxytocin/l and represented a stimulation of 670% over basal. PGF2α also stimulated the formation of [3H]IPs and the response at 1 μmol/l was a 204% stimulation over basal. The effects of PGF2α were independent of extracellular Ca2 + but the effect of oxytocin was reduced with low extracellular Ca2 +. Cyclic AMP formation, induced by forskolin or PGE2, had no effect on the stimulated levels of [3H]IPs. Pertussis toxin (PT) reduced the oxytocin-stimulated formation of [3H]IPs in a concentration-dependent manner. The maximal effect of PT resulted in an 80% reduction in the formation of [3H]IPs. However, PGF2α stimulation was not affected by PT treatment. To analyse the action of PT further, we studied its effect on oxytocin-induced changes in [Ca2 + ]i. The basal [Ca2 +]i was 112 ±4 nmol/l (n=225 cells) and was not affected by PT treatment (109 ± 3 nmol/l; n= 200 cells). In the absence of PT, 1 μmol oxytocin/l increased [Ca2 + ]i to a peak of 522 ±26 nmol/l, and in PT-treated cells, the [Ca2 + ]i peak was reduced to 348 ± 16 nmol/l. Similar inhibitory effects of PT were obtained at oxytocin concentrations ranging from 1 to 100 nmol/l. Our data suggest that in human myometrial cells, the oxytocin-induced production of [3H]IPs and increase in [Ca2 + ]i are mediated by a PT-sensitive G-protein. However, a significant fraction of the oxytocin response appears to be mediated by a PT-insensitive G-protein, possibly a member of the Gq family. Journal of Endocrinology (1993) 136, 497–509

scholarly journals Testosterone Induces an Intracellular Calcium Increase by a Nongenomic Mechanism in Cultured Rat Cardiac Myocytes

Endocrinology ◽  
2006 ◽  
Vol 147 (3) ◽  
pp. 1386-1395 ◽  
Author(s):  
Jose Miguel Vicencio ◽  
Cristian Ibarra ◽  
Manuel Estrada ◽  
Mario Chiong ◽  
Dagoberto Soto ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Androgen Receptor ◽  
Intracellular Calcium ◽  
Phospholipase C ◽  
G Protein ◽  
Cardiac Myocytes ◽  
Pertussis Toxin ◽  
Epifluorescence Microscopy ◽  
Inositol 1,4,5 Trisphosphate ◽  
Rat Cardiac Myocytes

Androgens are associated with important effects on the heart, such as hypertrophy or apoptosis. These responses involve the intracellular androgen receptor. However, the mechanisms of how androgens activate several membrane signaling pathways are not fully elucidated. We have investigated the effect of testosterone on intracellular calcium in cultured rat cardiac myocytes. Using fluo3-AM and epifluorescence microscopy, we found that exposure to testosterone rapidly (1–7 min) led to an increase of intracellular Ca2+, an effect that persisted in the absence of external Ca2+. Immunocytochemical analysis showed that these effects occurred before translocation of the intracellular androgen receptor to the perinuclear zone. Pretreatment of the cells with 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid-acetoxymethylester and thapsigargin blocked this response, suggesting the involvement of internal Ca2+ stores. U-73122, an inhibitor of phospholipase C, and xestospongin C, an inhibitor of inositol 1,4,5-trisphosphate receptor, abolished the Ca2+ signal. The rise in intracellular Ca2+ was not inhibited by cyproterone, an antagonist of intracellular androgen receptor. Moreover, the cell impermeant testosterone-BSA complex also produced the Ca2+ signal, indicating its origin in the plasma membrane. This effect was observed in cultured neonatal and adult rat cardiac myocytes. Pertussis toxin and the adenoviral transduction of β- adrenergic receptor kinase carboxy terminal peptide, a peptide inhibitor of βγ-subunits of G protein, abolished the testosterone-induced Ca2+ release. In summary, this is the first study of rapid, nongenomic intracellular Ca2+ signaling of testosterone in cardiac myocytes. Using various inhibitors and testosterone-BSA complex, the mechanism for the rapid, testosterone-induced increase in intracellular Ca2+ is through activation of a plasma membrane receptor associated with a Pertussis toxin-sensitive G protein-phospholipase C/inositol 1,4,5-trisphosphate signaling pathway.

scholarly journals A slowly ADP-ribosylated pertussis-toxin-sensitive GTP-binding regulatory protein is required for vasopressin-stimulated Ca2+ inflow in hepatocytes

1994 ◽  
Vol 299 (2) ◽  
pp. 399-407 ◽  
Author(s):  
L A Berven ◽  
B P Hughes ◽  
G J Barritt
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Single Cells ◽  
Regulatory Protein ◽  
Regulatory Proteins ◽  
Inositol Polyphosphates ◽  
Gtp Binding ◽  
Inositol 1,4,5 Trisphosphate ◽  
Epidermal Growth

The roles of heterotrimeric GTP-binding regulatory proteins (G-proteins) and inositol polyphosphates in the mechanism by which vasopressin stimulates Ca2+ inflow in hepatocytes were investigated by using single cells loaded with fura2 by microinjection. Vasopressin-stimulated Ca2+ inflow was mimicked by microinjection of guanosine 5′-[gamma-thio]triphosphate (GTP[S]) or guanosine 5′-[beta gamma-imido]triphosphate to the cells, but not adenosine 5′-[gamma-thio]triphosphate (ATP[S]) or guanosine 5′-[beta-thio]diphosphate (GDP[S]). Extracellular Gd3+ (5 microM) inhibited both vasopressin- and GTP[S]-stimulated Ca2+ inflow. GDP[S], but not GMP, administered to hepatocytes by microinjection, completely inhibited vasopressin-stimulated Ca2+ inflow and partially inhibited vasopressin-induced release of Ca2+ from intracellular stores. The microinjection of pertussis toxin had no effect either on the release of Ca2+ from intracellular stores or on Ca2+ inflow induced by vasopressin, but completely inhibited changes in these processes induced by epidermal growth factor (EGF). Hepatocytes isolated from rats treated with pertussis toxin for 24 h exhibited no vasopressin- or GTP[S]-stimulated Ca2+ inflow, whereas the vasopressin-stimulated release of Ca2+ from intracellular stores was similar to that observed for control cells. Heparin or ATP[S] inhibited, or delayed the onset of, both vasopressin-induced release of Ca2+ from intracellular stores and vasopressin-stimulated Ca2+ inflow. Vasopressin-induced oscillations in intracellular [Ca2+] were observed in some heparin-treated cells. It is concluded that the stimulation by vasopressin of Ca2+ inflow to hepatocytes requires inositol 1,4,5-trisphosphate (InsP3) and, by implication, the pertussis-toxin-insensitive G-protein required for the activation of phospholipase C beta [Taylor, Chae, Rhee and Exton (1991) Nature (London) 350, 516-518], and another G-protein which is slowly ADP-ribosylated by pertussis toxin and acts between InsP3 and the putative plasma-membrane Ca2+ channel. EGF-stimulated Ca2+ inflow involves at least one G-protein which is rapidly ADP-ribosylated and is most likely required for InsP3 formation.

Adenosine modulates voltage-gated Ca2+ channels in adult rat sympathetic neurons

1993 ◽  
Vol 70 (2) ◽  
pp. 610-620 ◽  
Author(s):  
Y. Zhu ◽  
S. R. Ikeda
Keyword(s):  
G Protein ◽  
Pertussis Toxin ◽  
Adenosine Receptor ◽  
Sympathetic Neurons ◽  
Current Component ◽  
Tail Current ◽  
Adult Rat ◽  
Selective Agonist ◽  
Voltage Dependent ◽  
Ca2 Channels

1. Ca(2+)-channel modulation by adenosine was investigated in enzymatically dispersed adult rat superior cervical ganglion (SCG) neurons using the whole-cell variant of the patch-clamp technique. 2. Adenosine produced a concentration-dependent decrease in the Ca(2+)-current amplitude with an EC50 of 174 nM and maximum inhibition of 36%. The effects of adenosine on the Ca2+ current were both time and voltage dependent. The inhibition was maximal at +10 mV and decreased at either hyperpolarizing or depolarizing potentials. 3. The inhibitory response desensitized after prolonged (> 1 min) exposure to 10 microM adenosine, whereas multiple brief (< 30 s) applications slightly decreased the subsequent response. 4. Adenosine-induced Ca2+ current inhibition was mediated by an A1-type adenosine receptor, because the half-maximal inhibition value for an A1 receptor selective agonist, chloro-N-cyclopentyladenosine, was 1,000-fold lower than that for an A2 receptor selective agonist, 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarbozamido adenosine hydrochloride (33 nM vs. 40 microM, respectively). 5. A guanine nucleotide binding protein (G protein) appeared to be involved in the action of adenosine, because: 1) the adenosine-induced current inhibition could be largely relieved by depolarizing voltage prepulses; 2) tail current analysis revealed that adenosine shifted Ca(2+)-channel activation to more depolarized potentials; and 3) adenosine inhibition was abolished by 2 mM intracellular guanosine 5'-O-(2-thiodiphosphate) or 500 ng/ml pertussis toxin pretreatment. 6. Adenosine did not appear to inhibit L-type Ca2+ channels, because the prolonged tail current component induced by the dihydropyridine "agonist" 2,6-dimethy-3-carbomethoxy-5-nitro-4-(2-trifluoromethyl-phenyl)- 1,4-dihydropyridine (2 microM) was not affected by adenosine. 7. Adenosine-induced inhibition was reduced to approximately 15% after application of 10 microM omega-conotoxin GVIA, suggesting that adenosine primarily inhibits N-type Ca2+ channels. The Ca(2+)-current component resistant to omega-conotoxin GVIA was also resistant to omega-agatoxin IVA (200 nM), suggesting a lack of P-type of Ca2+ channels in SCG neurons. 8. In conclusion, adenosine produces a dose-, time-, and voltage-dependent inhibition of Ca2+ currents in SCG neurons. Adenosine acts on an A1 adenosine receptor subtype in SCG neurons via a pertussis toxin-sensitive G protein to inhibit N-type Ca2+ channels and an unidentified Ca(2+)-current component. Modulation of Ca2+ currents by adenosine may be an important mechanism for its inhibitory effect on neurotransmitter release in sympathetic neurons.

Sign in / Sign up

Export Citation Format

Share Document