inositol-1-4-5-trisphosphate and verlukast

The purpose of this study is to identify the membrane transport machinery and cell signaling involved in the neurokinin A-inducible release of adenosine triphosphate (ATP) as an autocrine/paracrine signal from cultured guinea-pig taenia coli (T. coli) smooth muscle cells (SMCs). ATP release evoked by neurokinin A was inhibited by L-659877, a NK(2)-receptor antagonist; by modulators for Ins(1,4,5)P(3)-sensitive Ca(2+)-signaling, U-73122, thapsigargin, and 2-APB; and by W-7, a calmodulin inhibitor, and staurosporine, a protein kinase C (PKC) inhibitor, but not by wortmannin, a phosphoinositide 3-kinase inhibitor. The evoked release was suppressed by a multidrug resistance protein (MRP)-transporter inhibitors, MK-571, indomethacin, and benzbromarone, but not by CFTR-inh 172, a CFTR-Cl(-) channel blocker, and α-glycyrrhetinic acid, a gap junction hemichannel blocker. Neurokinin A caused a marked accumulation of Ins(1,4,5)P(3) and an increase in [Ca(2+)](i) in the cultured cells. These findings suggest that stimulation of Gq/(11) protein-coupled NK(2) receptor with neurokinin A caused a substantial release of ATP from cultured T. coli SMCs and that the evoked release may be mediated by Ins(1,4,5)P(3)-sensitive Ca(2+)-signaling, further by PKC and Ca(2+)/calmodulin signals, and finally by an activation of MRP transporters as the membrane device.

Topics: Adenosine Triphosphate; Animals; ATP Binding Cassette Transporter, Subfamily B; Calcium Signaling; Cells, Cultured; GTP-Binding Protein alpha Subunits, Gq-G11; Guinea Pigs; Inositol 1,4,5-Trisphosphate; Male; Neurokinin A; Propionates; Protein Transport; Quinolines; Receptors, Neurokinin-2

With the use of fura 2 measurements in multiple and single cells, we examined whether cysteinyl leukotrienes (CysLT) mediate angiotensin II (ANG II)-evoked increases in cytosolic free Ca(2+) concentration ([Ca(2+)](i)) in neonatal rat cardiomyocytes. ANG II-evoked CysLT release peaked at 1 min. The angiotensin type 1 (AT(1)) antagonist losartan, but not the AT(2) antagonist PD-123319, attenuated the elevations in [Ca(2+)](i) and CysLT levels evoked by ANG II. Vasopressin and endothelin-1 increased [Ca(2+)](i) but not CysLT levels. The 5-lipoxygenase (5-LO) inhibitor AA-861 and the CysLT(1)-selective antagonist MK-571 reduced the maximal [Ca(2+)](i) responses to ANG II but not to vasopressin and endothelin-1. While MK-571 reduced the responses to leukotriene D(4) (LTD(4)), the dual CysLT antagonist BAY-u9773 completely blocked the [Ca(2+)](i) elevation to both LTD(4) and LTC(4). These data confirm that ANG II-evoked increases, but not vasopressin- and endothelin-1-evoked increases, in [Ca(2+)](i) involve generation of the 5-lipoxygenase metabolite CysLT. The inositol (1,4,5)-trisphosphate [Ins(1,4,5)P(3)] antagonist 2-aminoethoxydiphenyl borate attenuated the [Ca(2+)](i) responses to ANG II and LTD(4). Thus AT(1) receptor activation by ANG II is linked to CysLT-mediated Ca(2+) release from Ins(1,4,5)P(3)-sensitive intracellular stores to augment direct ANG II-evoked Ca(2+) mobilization in rat cardiomyocytes.

Topics: Angiotensin II; Angiotensin Receptor Antagonists; Animals; Animals, Newborn; Arginine Vasopressin; Benzoquinones; Calcium; Cysteine; Endothelin-1; Enzyme Inhibitors; Fluorescent Dyes; Fura-2; Heart; Imidazoles; Inositol 1,4,5-Trisphosphate; Leukotriene C4; Leukotriene D4; Leukotrienes; Lipoxygenase Inhibitors; Losartan; Myocardium; Propionates; Pyridines; Quinolines; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Spectrometry, Fluorescence

Regulation of capacitative Ca(2+) entry was studied in two different multidrug resistance (MDR) protein (MRP1) overexpressing cell lines, HT29(col) and GLC4/ADR. MRP1 overexpression was accompanied by a decreased response to thapsigargin. Moreover, inhibition of capacitative Ca(2+) entry by D, L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) was abolished in MRP1 overexpressing cells. Both PDMP and the MRP1 inhibitor MK571 greatly reduced InsP(3)-mediated (45)Ca(2+) release from intracellular stores in HT29 cells. Again, these effects were virtually abolished in HT29(col) cells. Our results point to a modulatory role of MRP1 on intracellular calcium concentration ([Ca(2+)](i)) homeostasis which may contribute to the MDR phenotype.

Topics: Adenocarcinoma; ATP-Binding Cassette Transporters; Calcium; Calcium Radioisotopes; Colonic Neoplasms; Gene Expression; Homeostasis; Humans; Inositol 1,4,5-Trisphosphate; Morpholines; Multidrug Resistance-Associated Proteins; Propionates; Quinolines; Thapsigargin; Tumor Cells, Cultured