9-(tetrahydro-2-furyl)-adenine and 6-anilino-5-8-quinolinedione

ATP can activate several Ca(2+) influx channels in vascular endothelial cells. For example, it stimulates TRPC channels via capacitative and noncapacitative Ca(2+) entry (CCE and non-CCE, respectively) mechanisms; it also directly acts on P2X purinoceptors, resulting in Ca(2+) influx. In the present study, we tested the hypothesis that cyclic nucleotide-gated (CNG) channels also contribute to ATP-induced non-CCE.. Two selective inhibitors of CNG channels, L-cis-diltiazem and LY-83583, and CNGA2-specific siRNA were used to study the involvement of CNGA2 in ATP-induced non-CCE in endothelial cells. Ca(2+) influx was studied using Ca(2+)-sensitive fluorescence dyes Fluo-3 and Fluo-4.. L-cis-diltiazem and LY-83583 markedly reduced ATP-induced non-CCE in 3 types of endothelial cells including the H5V endothelial cell line, the primary cultured bovine aortic endothelial cells and the endothelial cells within isolated mouse aortic strips. The CNGA2-specific siRNA also reduced the ATP-induced non-CCE in H5V endothelial cells. The Ca(2+) influx was inhibited by Rp-8-CPT-cAMPS, MDL-12330A, SQ-22536 and MRS-2179, but not by ODQ or NF-157. Taken together, the present study demonstrated that CNGA2 channels contribute to ATP-induced non-CCE in vascular endothelial cells. It is likely that ATP acts through P2Y(1)receptors and adenylyl cyclases to stimulate CNGA2.

Topics: Adenine; Adenosine Diphosphate; Adenosine Triphosphate; Adenylyl Cyclase Inhibitors; Adenylyl Cyclases; Aminoquinolines; Aniline Compounds; Animals; Calcium Channel Blockers; Calcium Signaling; Cattle; Cells, Cultured; Cyclic GMP; Cyclic Nucleotide-Gated Cation Channels; Diltiazem; Endothelial Cells; Enzyme Inhibitors; Imines; Male; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Purinergic P2 Receptor Antagonists; Receptors, Purinergic P2; Receptors, Purinergic P2Y1; RNA Interference; Thionucleotides; Time Factors; Transfection; Vasodilation; Xanthenes

Odor stimulation may excite or inhibit olfactory receptor neurons (ORNs). It is well established that the excitatory response involves a cyclic AMP (cAMP) transduction mechanism that activates a nonselective cationic cyclic nucleotide-gated (CNG) conductance, accompanied by the activation of a Ca2+-dependent Cl(-) conductance, both causing a depolarizing receptor potential. In contrast, odor inhibition is attributed to a hyperpolarizing receptor potential. It has been proposed that a Ca2+-dependent K+ (K(Ca)) conductance plays a key role in odor inhibition, both in toad and rat isolated olfactory neurons. The mechanism underlying odor inhibition has remained elusive. We assessed its study using various pharmacological agents and caged compounds for cAMP, Ca2+, and inositol 1,4,5-triphosphate (InsP3) on isolated toad ORNs. The odor-triggered K(Ca) current was reduced on exposing the cell either to the CNG channel blocker LY83583 (20 microM) or to the adenylyl cyclase inhibitor SQ22536 (100 microM). Photorelease of caged Ca2+ activated a Cl- current sensitive to niflumic acid (10 microM) and a K+ current blockable by charybdotoxin (20 nM) and iberiotoxin (20 nM). In contrast, photoreleased Ca2+ had no effect on cells missing their cilia, indicating that these conductances are confined to the cilia. Photorelease of cAMP induced a charybdotoxin-sensitive K+ current in intact ORNs. Photorelease of InsP3 did not increase the membrane conductance of olfactory neurons, arguing against a direct role of InsP3 in chemotransduction. We conclude that a cAMP cascade mediates the activation of the ciliary Ca2+-dependent K+ current and that the Ca2+ ions that activate the inhibitory current enter the cilia through CNG channels.

Topics: Adenine; Aminoquinolines; Animals; Anura; Cadaverine; Charybdotoxin; Complex Mixtures; Cyclic AMP; Drug Interactions; Electric Stimulation; Enzyme Inhibitors; In Vitro Techniques; Membrane Potentials; Models, Neurological; Neural Conduction; Neural Inhibition; Odorants; Olfactory Receptor Neurons; Patch-Clamp Techniques; Signal Transduction; Ultraviolet Rays

Our objective was to study the involvement of adenylate and guanylate cylases in spontaneous uterine contractions and inhibition induced by the opening of potassium channels.. Uterine rings from rats at mid and term gestation and from rats at term gestation in labor were suspended in organ chambers for isometric tension recording. Concentration-response relationships to an opener of adenosine triphosphate-dependent potassium channels, levcromakalim, or to an opener of calcium-dependent potassium channels, NS 1619, were studied in the absence and presence of inhibitors of adenylate cyclase (MDL 12330 A, 2 x 10(-5) mol/L; SQ 22536, 10(-4) mol/L) or guanylate cyclase (LY 83583,3 x 10(-6) mol/L).. MDL 12330 A and SQ 22536 accentuated contractions in rings from rats at mid gestation but not at term gestation or at term gestation in labor. LY 83583 inhibited contractions in the rings from all 3 groups. Levcromakalim was equally effective in inhibiting contractions of rings from all 3 groups. MDL 12330 A, but not SQ 22536, decreased sensitivity and maximal inhibition induced by levcromakalim (term gestation greater than mid gestation greater than term gestation in labor). LY 83583 decreased the sensitivity to and maximal inhibition induced by levcromakalim in rings from pregnant rats at mid gestation. NS 1619 attenuated contraction of rings from rats at mid gestation and, to a lesser extent, at term gestation but accentuated contractions in rings from animals at term gestation in labor. MDL 12330 A, but not SQ 22536 or LY 83583, attenuated the changes induced by NS 1619 in rings from all 3 groups.. (1) The influence of nucleotide cyclases on basal uterine contractility depends on gestational age. (2) The inhibition of uterine contractions that results from the opening of calcium-dependent potassium channels depends on adenylate cyclase, whereas that of adenosine triphosphate-dependent potassium channels depends on both adenylate and guanylate cyclases. 3. Activation of adenosine triphosphate-dependent potassium channels is more efficient than activation of calcium-dependent potassium channels. 4. The inhibition induced by calcium-dependent potassium channel openers, but not adenosine triphosphate-dependent potassium channel openers, decreases as pregnancy progresses, and at delivery the activation of spontaneous contractile activity is evident.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Adenylyl Cyclases; Aminoquinolines; Animals; Benzimidazoles; Cromakalim; Enzyme Inhibitors; Female; Guanylate Cyclase; In Vitro Techniques; Potassium Channels; Pregnancy; Pregnancy, Animal; Rats; Rats, Sprague-Dawley; Uterine Contraction

Unidirectional blue light directs the rhizoid-thallus axis in the apolar zygotes of Fucus and Pelvetia. Here, it is shown that blue light (but not red light) increased cyclic GMP levels of Pelvetia zygotes by about a factor of 2. When the increase in cyclic GMP was blocked by a guanylyl cyclase inhibitor, photopolarization was also blocked. Bathing the cells in a permeant cyclic GMP analog, which should tend to collapse intracellular cyclic GMP gradients, reduced the degree of photopolarization. Growing the cells in the dark in a gradient of the analog caused the rhizoids to tend to form on the low concentration side. It appears that the stimulation of the blue light photoreceptors on the side nearer the light activates guanylyl cyclase and results in a transcytoplasmic cyclic GMP gradient that is necessary for polarization.

Topics: 1-Methyl-3-isobutylxanthine; Adenine; Adenylyl Cyclase Inhibitors; Aminoquinolines; Cell Division; Cell Polarity; Cyclic GMP; Enzyme Inhibitors; Guanylate Cyclase; Light; Phaeophyceae; Phosphoric Diester Hydrolases; Zygote