Pregnancy enhances G protein activation and nitric oxide release from uterine arteries

2001 ◽  
Vol 280 (5) ◽  
pp. H2069-H2075 ◽  
Author(s):  
L. P. Thompson ◽  
C. P. Weiner
Keyword(s):  
Nitric Oxide ◽  
Cholera Toxin ◽  
G Protein ◽  
Pertussis Toxin ◽  
Nitric Oxide Synthase Inhibitor ◽  
Protein Activation ◽  
Nitric Oxide Release ◽  
G Protein Activation ◽  
Hormonal Modulation ◽  
Synthase Inhibitor

We hypothesized that pregnancy modulates receptor-mediated responses of the uterine artery (UA) by altering G protein activation or coupling. Relaxation and contraction to NaF (0.5–11.5 mM), acetylcholine (10−9–10−5 M), and bradykinin (10−12–3 × 10−5 M) were measured in isolated UA of pregnant and nonpregnant guinea pigs. Responses were measured in the presence and absence of either cholera toxin (2 μg/ml) or pertussis toxin (Gαs and Gαiinhibitors, respectively). NaF relaxation was endothelium dependent and nitro-l-arginine sensitive (a nitric oxide synthase inhibitor). Relaxation to NaF, acetylcholine, and bradykinin were potentiated by pregnancy. Cholera but not pertussis toxin increased relaxation to acetylcholine and bradykinin in UA from nonpregnant animals, had no effect in UA from pregnant animals, and abolished the pregnancy-induced differences in acetylcholine relaxation. Cholera toxin potentiated the bradykinin-induced contraction of UA of both pregnant and nonpregnant animals, whereas pertussis toxin inhibited contraction of UA from pregnant animals only. Therefore, pregnancy may enhance agonist-stimulated endothelium-dependent relaxation and bradykinin-induced contraction of UA by inhibiting GTPase activity or enhancing Gαs but not Gαi activation in pregnant animals. Thus the diverse effects of pregnancy on UA responsiveness may result from hormonal modulation of G proteins coupled to their specific receptors.

G-protein Activation Decreases Isoflurane Inhibition of N-type Ba2+Currents

2003 ◽  
Vol 99 (2) ◽  
pp. 392-399 ◽  
Author(s):  
Igor M. Nikonorov ◽  
Thomas J. J. Blanck ◽  
Esperanza Recio-Pinto
Keyword(s):  
Cholera Toxin ◽  
G Protein ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Volatile Anesthetic ◽  
Cell Voltage ◽  
Dependent Manner ◽  
Protein Activation ◽  
G Protein Activation ◽  
Voltage Dependent

Background G-protein activation mediates inhibition of N-type Ca2+ currents. Volatile anesthetics affect G-protein pathways at various levels, and activation of G-proteins has been shown to increase the volatile anesthetic potency for inhibiting the electrical-induced contraction in ileum. The authors investigated whether isoflurane inhibition of N-type Ba2+ currents was mediated by G-protein activation. Methods N-type Ba2+ currents were measured in the human neuronal SH-SY5Y cell line by using the whole cell voltage-clamp method. Results Isoflurane was found to have two effects on N-type Ba2+ currents. First, isoflurane reduced the magnitude of N-type Ba2+ currents to a similar extent (IC50 approximately 0.28 mm) in the absence and presence of GDPbetaS (a nonhydrolyzable GDP analog). Interestingly, GTPgammaS (a nonhydrolyzable GTP analog and G-protein activator) in a dose-dependent manner reduced the isoflurane block; 120 microm GTPgammaS completely eliminated the block of 0.3 mm isoflurane and reduced the apparent isoflurane potency by approximately 2.4 times (IC50 approximately 0.68 mm). Pretreatment with pertussis toxin or cholera toxin did not eliminate the GTPgammaS-induced protection against the isoflurane block. Furthermore, isoflurane reduced the magnitude of voltage-dependent G-protein-mediated inhibition of N-type Ba2+ currents, and this effect was eliminated by pretreatment with pertussis toxin or cholera toxin. Conclusions It was found that activation of G-proteins in a neuronal environment dramatically reduced the isoflurane potency for inhibiting N-type Ba2+ currents and, in turn, isoflurane affected the G-protein regulation of N-type Ba2+ currents.

Cell surface beta-1,4-galactosyltransferase-I activates G protein-dependent exocytotic signaling

Development ◽  
2001 ◽  
Vol 128 (5) ◽  
pp. 645-654
Author(s):  
X. Shi ◽  
S. Amindari ◽  
K. Paruchuru ◽  
D. Skalla ◽  
H. Burkin ◽  
...  
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Zona Pellucida ◽  
Acrosome Reaction ◽  
Cytoplasmic Domain ◽  
Protein Activation ◽  
Acrosomal Exocytosis ◽  
G Protein Activation ◽  
Galactosyltransferase I

ZP3 is a protein in the mammalian egg coat (zona pellucida) that binds sperm and stimulates acrosomal exocytosis, enabling sperm to penetrate the zona pellucida. The nature of the ZP3 receptor/s on sperm is a matter of considerable debate, but most evidence suggests that ZP3 binds to beta-1,4-galactosyltransferase-I (GalTase) on the sperm surface. It has been suggested that ZP3 induces the acrosome reaction by crosslinking GalTase, activating a heterotrimeric G protein. In this regard, acrosomal exocytosis is sensitive to pertussis toxin and the GalTase cytoplasmic domain can precipitate G(i) from sperm lysates. Sperm from mice that overexpress GalTase bind more soluble ZP3 and show accelerated G protein activation, whereas sperm from mice with a targeted deletion in GalTase have markedly less ability to bind soluble ZP3, undergo the ZP3-induced acrosome reaction, and penetrate the zona pellucida. We have examined the ability of GalTase to function as a ZP3 receptor and to activate heterotrimeric G proteins using Xenopus laevis oocytes as a heterologous expression system. Oocytes that express GalTase bound ZP3 but did not bind other zona pellucida glycoproteins. After oocyte maturation, ZP3 or GalTase antibodies were able to trigger cortical granule exocytosis and activation of GalTase-expressing eggs. Pertussis toxin inhibited GalTase-induced egg activation. Consistent with G protein activation, both ZP3 and anti-GalTase antibodies increased GTP-gamma[(35)S] binding as well as GTPase activity in membranes from eggs expressing GalTase. Finally, mutagenesis of a putative G protein activation motif within the GalTase cytoplasmic domain eliminated G protein activation in response to ZP3 or anti-GalTase antibodies. These results demonstrate directly that GalTase functions as a ZP3 receptor and following aggregation, is capable of activating pertussis toxin-sensitive G proteins leading to exocytosis.

Stereoselective Differences in the Vasorelaxing Effects of S(+) and R(-) Ketamine on Rat Isolated Aorta 

1998 ◽  
Vol 88 (3) ◽  
pp. 718-724 ◽  
Author(s):  
Adriani Kanellopoulos ◽  
Gunther Lenz ◽  
Bernd Muhlbauer
Keyword(s):  
Nitric Oxide ◽  
Adenosine Triphosphate ◽  
Blocking Agent ◽  
Rat Aorta ◽  
K Channel ◽  
Nitric Oxide Synthase Inhibitor ◽  
Nitric Oxide Release ◽  
Racemic Ketamine ◽  
Synthase Inhibitor

Background S(+) ketamine, because of its higher anesthetic potency and lower risk of psychotomimetic reactions, has been suggested to be superior to presently available racemic ketamine. The racemate is a direct vasodilator in vivo, and thus the authors investigated the vasorelaxing effects of ketamine enantiomers on rat aorta. Methods Rat isolated aortic rings with and without endothelium were contracted with 3 x 10(-7) M norepinephrine. Then 10(-5) to 3 x 10(-3) M S(+), R(-), or racemic ketamine were added cumulatively. Vascular responses to ketamine were further studied in rings pretreated with the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine (NNLA), the adenosine triphosphate-sensitive K+ channel antagonist glibenclamide, and the L-type calcium channel blocking agent D888. Results Ketamine enantiomers and the racemate produced concentration-dependent vasorelaxation. The relaxing effect of S(+) ketamine was significantly weaker compared with R(-) ketamine and the racemate reflected by the half-maximum effective concentration (EC50) values of 11.6 x 10(-4), 4.8 x 10(-4), and 6 x 10(-4) M, respectively. Removal of the endothelium and NNLA or glibenclamide pretreatment did not significantly alter the vasorelaxing effect of ketamine. In contrast, D888 pretreatment significantly shifted the concentration-effect curves of both S(+) and R(-) ketamine rightward (EC50 values of 18.9 x 10(-4) and 8.5 x 10(-4) M, respectively), whereas the difference between the isomers was not affected. Conclusions Vasorelaxation by ketamine enantiomers is quantitatively stereoselective: The effect of S(+)ketamine is significantly weaker compared with that of the racemate and R(-) ketamine. This stereoselective difference is not due to nitric oxide release, activation of adenosine triphosphate-sensitive potassium channels, or differential inhibition of L-type calcium channels.

Role of G proteins in shear stress-mediated nitric oxide production by endothelial cells

1994 ◽  
Vol 267 (3) ◽  
pp. C753-C758 ◽  
Author(s):  
M. J. Kuchan ◽  
H. Jo ◽  
J. A. Frangos
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cells ◽  
Shear Stress ◽  
G Protein ◽  
G Proteins ◽  
No Production ◽  
Dependent Manner ◽  
Protein Activation ◽  
Synthase Inhibitor

Exposure of cultured endothelial cells to shear stress resulting from well-defined fluid flow stimulates the production of nitric oxide (NO). We have established that an initial burst in production is followed by sustained steady-state NO production. The signal transduction events leading to this stimulation are not well understood. In the present study, we examined the role of regulatory guanine nucleotide binding proteins (G proteins) in shear stress-mediated NO production. In endothelial cells not exposed to shear stress, AIF4-, a general activator of G proteins, markedly elevated the production of guanosine 3',5'-cyclic monophosphate (cGMP). Pretreatment with NO synthase inhibitor N omega-nitro-L-arginine completely blocked this stimulation. Incubation with guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), a general G protein inhibitor, blocked the flow-mediated burst in cGMP production in a dose-dependent manner. Likewise, GDP beta S inhibited NOx (NO2 + NO3) production for the 1st h. However, inhibition was not detectable between 1 and 3 h. Pertussis toxin (PTx) had no effect on the shear response at any time point. The burst in NO production caused by a change in shear stress appears to be dependent on a PTx-refractory G protein. Sustained shear-mediated production is independent of G protein activation.

scholarly journals Enhanced IPC by activation of pertussis toxin-sensitive and -insensitive G protein-coupled purinoceptors

2002 ◽  
Vol 282 (5) ◽  
pp. H1933-H1943 ◽  
Author(s):  
Hideki Ninomiya ◽  
Hajime Otani ◽  
Kejie Lu ◽  
Takamichi Uchiyama ◽  
Masakuni Kido ◽  
...  
Keyword(s):  
G Protein ◽  
Pertussis Toxin ◽  
Myocardial Protection ◽  
Kinase Inhibitor ◽  
Left Ventricular ◽  
Nitric Oxide Synthase Inhibitor ◽  
Protein Kinase C Inhibitor ◽  
Synthase Inhibitor ◽  
Oxide Synthase ◽  
G Protein Coupled

Extracellular ATP plays an important role in ischemic preconditioning (IPC) through the activation of P2y purinoceptors. This study examined whether ATP-stimulated P2y purinoceptors are coupled to pertussis toxin (PTX)-insensitive G protein and whether activation of this pathway enhances myocardial protection afforded by IPC. The rat was treated with PTX for 48 h, and the heart was then isolated and buffer perfused. The heart underwent IPC by three cycles of 5-min ischemia and 5-min reperfusion before 25 min of global ischemia. Isovolumic left ventricular function was measured, and functional recovery at 30 min after reperfusion was taken as an end point of myocardial protection. PTX pretreatment partially inhibited functional protection by IPC. Treatment with 100 μM 8-( p-sulfophenyl) theophylline (SPT) during IPC had no further effect on PTX-induced inhibition of functional protection by IPC, whereas suramin (300 μM) or reactive blue (RB) (10 μM) completely abolished myocardial protection in the preconditioned heart pretreated with PTX. Supplementation with adenosine (30 μM), ATP (30 μM), or UTP (50 μM) significantly enhanced IPC-induced functional protection, although preconditioning with these nucleotides without IPC had no protective effect. Adenosine-enhanced IPC was inhibited by pretreatment with PTX and SPT but not by suramin or RB, whereas ATP-enhanced IPC was inhibited by suramin or RB in combination with PTX pretreatment. On the other hand, UTP-enhanced IPC was not affected by PTX pretreatment but was inhibited by suramin or RB. Adenosine supplemented IPC without PTX pretreatment and ATP supplemented IPC with PTX pretreatment were not affected by nitric oxide synthase inhibitor N ω-nitro-l-arginine methyl ester (100 μM). Although the protein kinase C inhibitor Ro318425 (0.3 μM) or tyrosine kinase inhibitor genistein (50 μM) had no significant effect on the functional protection afforded by adenosine-supplemented IPC without PTX pretreatment and ATP-supplemented IPC with PTX pretreatment, the combination of Ro318425 and genistein attenuated functional protection afforded by both the purinoceptor agonist-supplemented IPC. These results suggest the crucial involvement of PTX-sensitive and -insensitive G protein coupled purinoceptors in enhanced IPC by supplementation with adenosine, ATP, and UTP.

scholarly journals P2 Purinoceptor Saturation by Adenosine Triphosphate Impairs Renal Autoregulation in Dogs

1999 ◽  
Vol 10 (3) ◽  
pp. 492-498
Author(s):  
DEWAN S. A. MAJID ◽  
EDWARD W. INSCHO ◽  
L. GABRIEL NAVAR
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Sodium Excretion ◽  
Nitric Oxide Synthase Inhibitor ◽  
Nitric Oxide Release ◽  
Renal Autoregulation ◽  
Mediated Effects ◽  
P2 Purinoceptors ◽  
Before And After ◽  
Synthase Inhibitor

Abstract. Recent studies have suggested a role for P2 purinoceptors on vascular smooth muscle cells in the mechanism of renal autoregulation. Experiments were performed in anesthetized dogs (n = 9) to examine renal blood flow (RBF) auto-regulatory efficiency before and after saturation of P2 purinoceptors with acute intra-arterial administration of ATP (1 mg/kg per min). Dogs were pretreated with the nitric oxide synthase inhibitor nitro-L-arginine (NLA) (50 μg/kg per min), to avoid endothelial P2 receptor-mediated effects on nitric oxide release caused by the intra-arterial ATP infusions. NLA treatment decreased RBF (5.3 ± 0.3 to 3.6 ± 0.2 ml/min per g) and sodium excretion (3.6 ± 0.4 to 0.9 ± 0.2 ml/min per g) without producing significant changes in GFR (0.92 ± 0.04 to 0.90 ± 0.06 ml/min per g) or RBF autoregulatory efficiency. ATP administration to NLA-treated dogs resulted in further decreases in RBF (2.8 ± 0.2 ml/min per g), GFR (0.58 ± 0.05 ml/min per g), and sodium excretion (0.6 ± 0.2 μmol/min per g). In addition, there was marked impairment of RBF autoregulatory efficiency during ATP infusion. The slopes of the arterial pressure-blood flow relationships at renal arterial pressures of >75 mmHg were significantly altered, from 0.003 ± 0.001 to 0.2 ± 0.002 ml/min per g per mmHg. Discontinuation of ATP infusion restored RBF autoregulatory efficiency. Norepinephrine (5 μg/kg per min) administration in these NLA-treated dogs decreased RBF (2.5 ± 0.3 ml/min per g; n = 4) to a similar extent, compared with ATP, but did not impair RBF autoregulation. These results support the hypothesis that P2 purinoceptors may be involved in mediating autoregulatory adjustments in renal vascular resistance.

Extravascular adenosine influences endothelium-derived nitric oxide release from perfused dog semitendinosus artery

1998 ◽  
Vol 76 (2) ◽  
pp. 90-98 ◽  
Author(s):  
N Woodley ◽  
J K Barclay
Keyword(s):  
Nitric Oxide ◽  
Skeletal Muscle ◽  
Superoxide Dismutase ◽  
Bicarbonate Buffer ◽  
Nitric Oxide Synthase Inhibitor ◽  
Nitric Oxide Release ◽  
Adenosine Receptor Antagonist ◽  
Synthase Inhibitor ◽  
Oxide Synthase ◽  
Endothelium Dependent Relaxation

We tested the hypothesis that extravascular adenosine induces the release of vasodilatory products from endothelial cells lining skeletal muscle vessels. Endothelium-intact (n = 35) and -denuded (n = 5) dog semitendinosus intramuscular arteries were isolated, cannulated, and placed in 100-mL baths containing Krebs-Henseleit bicarbonate buffer (Krebs) at 37°C and gassed with 95% O2- 5% CO2. Each vessel, as well as a parallel tubing segment (avascular control), was perfused at 3.5 ± 0.2 mL/min (inflow pressure 94 ± 2 mmHg; 1 mmHg = 133.3 Pa) with Krebs containing 100 µM phenylephrine, 6% dextran, and 15 units/mL superoxide dismutase. Perfusate from all segments dripped onto endothelium-denuded dog femoral artery rings. The addition of 10 µM acetylcholine to the perfusate to test the functional integrity of endothelium-intact donor segments did not alter resistance in vessel segments or change force in rings. The addition of 100 µM adenosine to the extravascular bath decreased resistance 1.5 ± 0.4 mmHg ·mL-1·min-1in vessel segments but was without effect on downstream rings. When acetylcholine was retested in the presence of extravascular adenosine, a relaxation (16 ± 6%) occurred in rings receiving perfusate from endothelium-intact segments but not endothelium-denuded or tubing segments. This relaxation was eliminated by Nomega-nitro-L-arginine (10 µM), a nitric oxide synthase inhibitor, and was attenuated to 4 ± 1% by 8-phenyltheophylline (10 µM), an adenosine receptor antagonist. Thus adenosine, in conjunction with acetylcholine, acting through a receptor-mediated event, resulted in the release of nitric oxide from the endothelium of perfused intramuscular arteries, indicating the potential for extravascular conditions to influence the release of endothelium-derived products.Key words: acetylcholine, adenosine, endothelium-dependent relaxation, nitric oxide, perfused intramuscular artery.

scholarly journals Stimulation of high-affinity GTPase activity and cholera toxin-catalysed [32P]ADP-ribosylation of Gi by lysophosphatidic acid (LPA) in wild-type and α2C10 adrenoceptor-transfected Rat 1 fibroblasts

1994 ◽  
Vol 298 (2) ◽  
pp. 493-497 ◽  
Author(s):  
C Carr ◽  
M Grassie ◽  
G Milligan
Keyword(s):  
Cholera Toxin ◽  
G Protein ◽  
Pertussis Toxin ◽  
Lysophosphatidic Acid ◽  
Gtpase Activity ◽  
Response Curves ◽  
Protein Activation ◽  
Adp Ribosylation ◽  
High Affinity ◽  
Stimulation Of

Lysophosphatidic acid (LPA) stimulated high-affinity GTPase activity in membranes of Rat 1 fibroblasts. This effect was dose-dependent, with maximal effects at 10 microM LPA, and was attenuated by pertussis toxin but not by cholera toxin pretreatment of the cells, indicating that the effect was likely to be produced by a Gi-like G-protein. LPA stimulation of high-affinity GTPase was also observed in a clone of Rat 1 fibroblasts that had been transfected to express the human alpha 2C10 adrenoceptor. The alpha 2 adrenoceptor agonist UK14304 also stimulated high-affinity GTPase activity in membranes of these cells, but not in parental Rat 1 cells. LPA was also able to promote cholera toxin-catalysed [32P]ADP-ribosylation of Gi. This effect of LPA was also prevented by pretreatment of the cells with pertussis toxin but not cholera toxin. LPA-stimulated cholera toxin-catalysed [32P]ADP-ribosylation of Gi in membranes of the alpha 2C10 adrenoceptor-expressing clone was additive with that produced by UK14304. Dose-response curves for LPA in the two assays of G-protein activation were coincident. The results presented herein demonstrate conclusively that the pertussis toxin-sensitive effects of LPA in Rat 1 fibroblasts and a clone of these cells expressing the alpha 2C10 adrenoceptor are produced directly by the activation of Gi.

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