scholarly journals Two ATP-activated conductances in bullfrog atrial cells.

1988 ◽  
Vol 91 (1) ◽  
pp. 1-27 ◽  
Author(s):  
D D Friel ◽  
B P Bean
Keyword(s):  
Ionic Channels ◽  
Extracellular Atp ◽  
Fluctuation Analysis ◽  
Current Fluctuation ◽  
Atrial Cells ◽  
Atp Analogues ◽  
Alpha Beta ◽  
Gamma S ◽  
Inwardly Rectifying ◽  
Current Fluctuation Analysis

Currents activated by extracellular ATP were studied in single voltage-clamped bullfrog atrial cells. Rapid application of ATP elicited currents carried through two different conductance pathways: a rapidly desensitizing conductance reversing near -10 mV, and a maintained, inwardly rectifying conductance reversing near -85 mV. ATP activated the desensitizing component of current with a K 1/2 of approximately 50 microM and the maintained component with a K 1/2 of approximately 10 microM. Both types of current were activated by ATP but not by adenosine, AMP, or ADP. The desensitizing current was selectively inhibited by alpha, beta-methylene ATP, and the maintained, inwardly rectifying current was selectively suppressed by extracellular Cs. The desensitizing component of current was greatly reduced when extracellular Na was replaced by N-methylglucamine, but was slightly augmented when Na was replaced by Cs. GTP, ITP, and UTP were all ineffective in activating the desensitizing current, and of a variety of ATP analogues, only ATP-gamma-S was effective. Addition of EGTA or BAPTA to the intracellular solution did not obviously affect the desensitizing current. Fluctuation analysis of currents through the desensitizing conductance suggested that current is carried through ionic channels with a small (less than pS) unitary conductance.

scholarly journals Current Fluctuation Analysis to Study Mg2+-Binding in the Bacterial Porin OmpF

2013 ◽  
Vol 104 (2) ◽  
pp. 630a
Author(s):  
María Queralt Martín ◽  
Antonio Alcaraz ◽  
Vicente M. Aguilella
Keyword(s):  
Fluctuation Analysis ◽  
Current Fluctuation ◽  
Current Fluctuation Analysis

scholarly journals Receptor current fluctuation analysis in the labellar sugar receptor of the fleshfly.

1988 ◽  
Vol 91 (1) ◽  
pp. 29-47 ◽  
Author(s):  
H Kijima ◽  
K Nagata ◽  
A Nishiyama ◽  
H Morita
Keyword(s):  
Time Constant ◽  
Receptor Cell ◽  
Process Analysis ◽  
Power Spectra ◽  
Sugar Concentration ◽  
Fluctuation Analysis ◽  
Current Fluctuation ◽  
Sugar Receptor ◽  
Current Fluctuation Analysis ◽  
Sensory Process

Fluctuations in the receptor current of the labellar sugar receptor of the fleshfly were analyzed. The receptor current was recorded extracellularly as a drop in potential between the tip and the base of the taste sensillum. After treatment with tetrodotoxin, the taste cells completely lost their impulses but retained their receptor currents, thus facilitating analysis of the receptor current without disturbance by impulses. The current fluctuation increased markedly when the sensillum was stimulated with effective sugars: maltose, sucrose, and fructose. The fluctuation increased in parallel with development of the receptor current, which indicates that it occurs as soon as the sugar reaches the apex of the sensory process. Analysis of fluctuations by computation of autocorrelation functions (ACFs) or power spectra (PS) revealed that: (a) the variance (mean square) of fluctuation vs. sugar concentration curve reached a maximum, in contrast to the monotonic increase shown by the receptor current; (b) the ACF was approximated by an exponential term, and its time constant differed according to the sugars used and their concentrations. The time constants for fructose and maltose decreased with increases in sugar concentration. At the concentrations of sugars evoking the same magnitude of receptor current, the time constant for fructose was the largest and that for maltose was the smallest. It was strongly suggested that transduction ion channels are present at the tip region of the sensory process of the sugar receptor cell and are operated directly by sugars.

Extracellular ATP stimulates proliferation of cultured mesangial cells via P2-purinergic receptors

1992 ◽  
Vol 263 (3) ◽  
pp. F374-F383 ◽  
Author(s):  
E. Schulze-Lohoff ◽  
S. Zanner ◽  
A. Ogilvie ◽  
R. B. Sterzel
Keyword(s):  
Mesangial Cells ◽  
Inositol Phosphates ◽  
Rank Order ◽  
Secretory Activity ◽  
Fold Increase ◽  
Extracellular Atp ◽  
Thymidine Uptake ◽  
Cell Counts ◽  
Atp Analogues ◽  
Gamma S

We examined the role of the platelet product ATP in regulating replication and secretory activity of cultured rat mesangial cells (MCs). Extracellular ATP (25-100 microM) significantly increased [3H]thymidine uptake of growth-arrested MCs 2.1-fold; cell counts increased by 35.1%. Addition of ATP to MCs in combination with other platelet products, such as platelet-derived growth factor, isoform BB (100 ng/ml), and serotonin (1 microM), resulted in strong synergistic mitogenicity (up to 45.6-fold over control). As immediate signaling events following stimulation with ATP, we found increased production of inositol phosphates (3.2-fold increase for inositol bisphosphate and 1.6-fold increase for inositol trisphosphate by 30 s) and release of prostaglandin E2 (PGE2, 9.2-fold increase by 5 min). When we studied the rank order of potency of various ATP analogues for the production of inositol phosphates and PGE2, ATP, UTP, and adenosine 5'-O-(3-thio)triphosphate (ATP gamma S) were the most potent agonists. Although ATP and ATP gamma S were also strong mitogens, UTP was not. Additional inhibitor studies indicated that protein kinase C or cyclooxygenase products were not involved in the mitogenic effects of ATP. In summary, the major platelet product ATP is a potent comitogen for cultured MCs and strongly synergizes with other growth factors. The experiments with ATP analogues point to different receptors mediating mitogenesis, generation of inositol phosphates, and PGE2 production. The precise mechanism of the mitogenic action of ATP on MCs remains to be characterized.

An ATP-activated nonselective cation channel in guinea pig ventricular myocytes

1995 ◽  
Vol 269 (3) ◽  
pp. H789-H797 ◽  
Author(s):  
K. E. Parker ◽  
A. Scarpa
Keyword(s):  
Guinea Pig ◽  
Chloride Channels ◽  
Cardiac Electrophysiology ◽  
Ventricular Myocytes ◽  
Traumatic Injury ◽  
Reversal Potential ◽  
Extracellular Atp ◽  
Fluctuation Analysis ◽  
Inward Current ◽  
Inwardly Rectifying

Extracellular ATP released from nerves onto vascular smooth muscle or released from damaged tissues during traumatic injury, shock, or ischemia profoundly alters cardiovascular physiology. We have used patch-clamp methods to investigate the effects of extracellular ATP on guinea pig ventricular myocytes because guinea pigs are a commonly used model for the study of cardiac electrophysiology. We have found that ATP activates a rapid, desensitizing, inward current. This inward current is activated by a P2 receptor that does not conform to published receptor subclasses. A concentration of 100 microM ATP activates more current than 100 microM alpha, beta-methyleneadenosine 5'-triphosphate, which in turn activates more current than 100 microM ADP. 2-Methylthioadenosine 5'-triphosphate (2-MeS-ATP) and adenosine 5'-O-(3-thiotriphosphate) are also effective agonists. Adenosine, AMP, guanosine 5'-triphosphate, and uridine 5'-triphosphate are ineffective at 100 microM. The inward conductance has a reversal potential near 0 mV and in ion-substitution experiments was found to be carried through nonselective cation channels rather than chloride channels. The conductance has inwardly rectifying current-voltage (I-V) relations. When ATP is used as the agonist, fluctuation analysis yields an apparent unitary conductance of 0.08 pA at a holding potential of -120 mV with sodium as the main charge-carrying ion. The combination of inwardly rectifying I-V relations, the efficacy of 2-MeS-ATP, and the very low conductance distinguish this conductance from other ATP-activated nonselective channels, including those recently cloned from rat vas deferens and PC-12 cells.

scholarly journals Current Fluctuation Analysis in a Protein Nanopore

2015 ◽  
Vol 108 (2) ◽  
pp. 634a
Author(s):  
María Queralt-Martín ◽  
M. Lidón López ◽  
Vicente M. Aguilella ◽  
Antonio Alcaraz
Keyword(s):  
Fluctuation Analysis ◽  
Current Fluctuation ◽  
Current Fluctuation Analysis
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