P2 purinoceptor localization along rat nephron and evidence suggesting existence of subtypes P2Y1 and P2Y2

1998 ◽  
Vol 274 (6) ◽  
pp. F1006-F1014 ◽  
Author(s):  
Seok Ho Cha ◽  
Takashi Sekine ◽  
Hitoshi Endou
Keyword(s):  
Calcium Concentration ◽  
Free Calcium ◽  
Dependent Manner ◽  
Reactive Blue 2 ◽  
Collecting Tubule ◽  
Single Nephron ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration ◽  
Dose Dependent ◽  
Cortical Collecting Tubule

Effects of extracellular ATP on intracellular free calcium concentration ([Ca2+]i) were examined in rat single nephron segments using the fura 2-AM. ATP (10 μM) induced a significant transient increase in [Ca2+]iin the glomerulus, the early proximal convoluted tubule (S1), the cortical collecting tubule (CCT), and the outer medullary collecting tubule (OMCT). The magnitude of the response was the greatest in the OMCT among four segments. ATP induced an increase in the [Ca2+]iin a dose-dependent manner in S1 and OMCT. In the OMCT, ATP caused a biphasic increase in [Ca2+]iconsisting of an initial rapid rise and a sustained phase. Removal of calcium from the medium resulted in an attenuation of the sustained phase of [Ca2+]iand an ∼30% reduction in the height of the initial [Ca2+]ipeak in response to 10 μM ATP. Effects of ATP, its analogs, and its metabolites were tested in the S1 and OMCT. ATP, 2-methylthio-ATP (2-MeS-ATP), ADP, and UTP increased [Ca2+]idose dependently. AMP and adenosine did not affect [Ca2+]iin the S1 and OMCT. The ATP- or 2-MeS-ATP-induced [Ca2+]iincrease was inhibited by the pretreatment of the S1 and OMCT with suramin or reactive blue 2. Neomycin, a phospholipase C inhibitor, attenuated the ATP-induced [Ca2+]iincrease. To investigate the hormonelike action of ATP in OMCT, a heterologous cross desensitization was performed. The pretreatment of OMCT with ATP inhibited increases in vasopressin-, ANG II-, endothelin-1-, or bradykinin-induced [Ca2+]iincrease. These findings suggest that ATP might affect the above peptidyl agonist-activated calcium mobilizations.

Endothelin 1 increases cell calcium in mouse collecting tubule cells

1991 ◽  
Vol 261 (4) ◽  
pp. F720-F725 ◽  
Author(s):  
M. Naruse ◽  
S. Uchida ◽  
E. Ogata ◽  
K. Kurokawa
Keyword(s):  
Free Calcium ◽  
Second Phase ◽  
Endothelin 1 ◽  
Single Nephron ◽  
Heterologous Desensitization ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration ◽  
Collecting Tubules ◽  
Dose Dependent ◽  
Homologous Desensitization

Effects of endothelin 1 (ET-1) on intracellular free calcium concentration ([Ca2+]i) were examined in superfused single-nephron segments dissected from mouse kidney. ET-1, 10(-9) to 10(-6) M, caused a biphasic increase in [Ca2+]i consisting of an initial rapid rise followed by a second more sustained elevation in [Ca2+]i in cortical collecting tubules (CCT), outer medullary CT (OMCT), and inner medullary CT (IMCT). The magnitude of the response was dose dependent and was greater in CCT than in OMCT or IMCT. Additional studies using CCT revealed that Ca2+ removal from the superfusate resulted in attenuation of the second phase of [Ca2+]i with approximately 50% reduction in the height of the initial [Ca2+]i peak in response to 10(-6) M ET-1. Ca2+ channel blocker nicardipine had little effect on ET-1-evoked changes in [Ca2+]i. BAY K 8644 and high superfusate K+ also did not affect [Ca2+]i. Addition of ET-1 and arginine vasopressin (AVP), 10(-6) M each, showed the presence of homologous desensitization but the absence of heterologous desensitization in [Ca2+]i changes. There was no additive effect of ET-1 and AVP on [Ca2+]i when they were added together. These data show that ET-1 evokes a biphasic increase in [Ca2+]i of collecting tubules and suggest that the initial peak of the ET-1-evoked rise in [Ca2+]i is largely due to cell Ca2+ release and that the second sustained rise in [Ca2+]i is largely due to increased Ca2+ influx. Data also suggest that ET-1 and AVP may act in the collecting tubules through different receptors.

Identification of ecto-PKC on surface of human platelets: role in maintenance of latent fibrinogen receptors

2000 ◽  
Vol 278 (6) ◽  
pp. H2008-H2019 ◽  
Author(s):  
Anna Babinska ◽  
Michael V. Hogan ◽  
Tomasz Sobocki ◽  
Malgorzata B. Sobocka ◽  
Yigal H. Ehrlich ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Calcium Concentration ◽  
Surface Protein ◽  
Human Platelets ◽  
Surface Proteins ◽  
Free Calcium ◽  
Platelet Surface ◽  
Inhibitory Peptides ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration

Human platelets express a protein phosphorylation system on their surface. A specific protein kinase C (PKC) antibody, monoclonal antibody (MAb) 1.9, which binds to the catalytic domain of PKC and inhibits its activity, causes the aggregation of intact platelets while inhibiting the phosphorylation of platelet surface proteins. Photoaffinity labeling with 100 nM 8-azido-[α32P]ATP identified this ecto-PKC as a single surface protein of 43 kDa sensitive to proteolysis by extracellular 0.0005% trypsin. Inhibition of the binding of 8-azido-[α32P]ATP to the 43-kDa surface protein by MAb 1.9 identified this site as the active domain of ecto-PKC. Covalent binding of the azido-ATP molecule to the 43-kDa surface protein inhibited the phosphorylative activity of the platelet ecto-PKC. Furthermore, PKC pseudosubstrate inhibitory peptides directly induced the aggregation of platelets and inhibited azido-ATP binding to the 43-kDa protein. Platelet aggregation induced by MAb 1.9 and by PKC inhibitory peptides required the presence of fibrinogen and resulted in an increase in the level of intracellular free calcium concentration. This increase in intracellular free calcium concentration induced by MAb 1.9 was found to be dependent on the binding of fibrinogen to activated GPIIb/IIIa integrins, suggesting that MAb 1.9 causes Ca2+flux through the fibrinogen receptor complex. We conclude that a decrease in the state of phosphorylation of platelet surface proteins caused by inhibition of ecto-PKC results in membrane rearrangements that can induce the activation of latent fibrinogen receptors, leading to platelet aggregation. Accordingly, the maintenance of a physiological steady state of phosphorylation of proteins on the platelet surface by ecto-PKC activity appears to be one of the homeostatic mechanisms that maintain fibrinogen receptors of circulating platelets in a latent state that cannot bind fibrinogen.

A cross-sectional study of basal platelet intracellular free calcium concentration in normotensive and hypertensive primigravid pregnancies

1990 ◽  
Vol 78 (1) ◽  
pp. 75-80 ◽  
Author(s):  
M. D. Kilby ◽  
F. Broughton Pipkin ◽  
S. Cockbill ◽  
S. Heptinstall ◽  
E. M. Symonds
Keyword(s):  
Calcium Concentration ◽  
Post Partum ◽  
Cross Sectional Study ◽  
Free Calcium ◽  
Sectional Study ◽  
Third Trimester ◽  
Cross Sectional ◽  
The Third ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration

1. The intracellular free calcium concentration ([Ca2+]i) in washed human platelets was measured using the fluorescent indicator, fura-2, in a cross-sectional study of 36 normotensive, primigravid volunteers, 12 in each trimester of pregnancy and a further 12 at 6 weeks post partum. The results were compared with those obtained from 30 normal female volunteers not using oral contraception. 2. The mean basal [Ca2+]i in the platelets of the pregnant women in the first two trimesters (115.6 ± 6.7 and 120.1 ± 5.7 nmol/l, respectively) was not shown to differ significantly from that of normal non-pregnant volunteers (112.3 ± 2.9 nmol/l). However, during the third trimester a significant increase in [Ca2+]i was noted (134.0 ± 4.9 nmol/l; P < 0.05), with a return to normal values in the post-partum period (108.2 ± 6.1 nmol/l). 3. [Ca2+]i was also measured in the platelets of a group of 12 primigravid pregnant women in the third trimester whose pregnancies were complicated by gestational hypertension (pregnancy-induced hypertension and preeclampsia). A significant rise in basal [Ca2+]i was noted in the platelets of primigravidae whose pregnancies were complicated by pre-eclampsia (163.6 ± 8.8 nmol/l) as compared with normotensive, third-trimester primigravidae (P < 0.02). However, no correlation could be demonstrated between [Ca2+]i and systemic blood pressure.

scholarly journals The effect of mitogenic lectins and monoclonal antibodies on intracellular free calcium concentration in human T-lymphocytes

1984 ◽  
Vol 219 (2) ◽  
pp. 661-666 ◽  
Author(s):  
K O'Flynn ◽  
D C Linch ◽  
P E R Tatham
Keyword(s):  
T Cells ◽  
Monoclonal Antibodies ◽  
T Cell ◽  
Calcium Concentration ◽  
Human Lymphocytes ◽  
Maximum Level ◽  
T Cell Response ◽  
Free Calcium ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration

The effect of mitogenic lectins and the mitogenic antibody UCHT1 on the cytoplasmic free Ca2+ concentration ([Ca2+]i) in human lymphocytes was investigated by using the fluorescent Ca2+-indicator quin2 . Phytohaemagglutinin, concanavalin A and UCHT1 increased [Ca2+]i in T-cells to a maximum level within 2 min. No T-cell response was seen with poke weed mitogen. None of the mitogens affected non-T-cell [Ca2+]i.

Vasopressin increases cytosolic free calcium in LLC-PK1 cells through a V1-receptor

1987 ◽  
Vol 253 (2) ◽  
pp. F328-F332 ◽  
Author(s):  
M. A. Burnatowska-Hledin ◽  
W. S. Spielman
Keyword(s):  
Parathyroid Hormone ◽  
Arginine Vasopressin ◽  
Calcium Concentration ◽  
Mdck Cells ◽  
Free Calcium ◽  
Base Line ◽  
Cytosolic Free Calcium ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
Dose Dependent

We examined the effects of arginine vasopressin (AVP), parathyroid hormone (PTH), and bradykinin (BK) on the cytosolic free calcium concentration ([Ca]i) in cultured LLC-PK1 and MDCK kidney cell lines by use of the fluorescent Ca chelator fura-2. In LLC-PK1 cells, the addition of AVP but not [1-desamino-8-D-arginine]vasopressin (dDAVP, V2 agonist), PTH, or BK (10(-6) M) caused a significant increase in [Ca]i. The AVP-induced increase in [Ca]i from 61 +/- 6 to 225 +/- 44 nM (n = 7, P less than 0.01) was rapid and transient, returning to base line in 2 to 3 min. The effect of AVP was dose dependent and was present at 1 (61% increase) but not 5 min after extracellular Ca was removed. The effect of 10(-6) M AVP could be blocked with the pressor (V1) antagonist, d(CH2)5Tyr(Me)AVP, but not dDAVP. In MDCK cells, BK, but not AVP and PTH, increased [Ca]i from 146 +/- 11 to 281 +/- 31 nM (n = 9, P less than 0.001). The removal of extracellular Ca (5 min), reduced but did not abolish this effect. These results indicate that [Ca]i mobilized by activation of V1-receptors may mediate AVP-regulated function in some transporting epithelia.

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