cyclic-gmp and gadolinium-chloride

Nitric oxide (NO) production during hyposmotic stimulation in outer hair cells (OHCs) of the guinea pig cochlea was investigated using the NO sensitive dye DAF-2. Simultaneous measurement of the cell length and NO production showed rapid hyposmotic-induced cell swelling to precede NO production in OHCs. Hyposmotic stimulation failed to induce NO production in the Ca2+-free solution. L-NG-nitroarginine methyl ester (L-NAME), a non-specific NO synthase inhibitor and gadolinium, a stretch-activated channel blocker inhibited the hyposmotic stimulation-induced NO production whereas suramin, a P2 receptor antagonist did not. S-nitroso-N-acetylpenicillamine (SNAP), a NO donor inhibited the hyposmotic stimulation-induced increase in the intracellular Ca2+ concentrations ([Ca2+]i) while L-NAME enhanced it. 1H-[1,2,4]oxadiazole[4,3a]quinoxalin-1-one, an inhibitor of guanylate cyclase and KT5823, an inhibitor of cGMP-dependent protein kinase (PKG) mimicked effects of L-NAME on the Ca2+ response. Transient receptor potential vanilloid 4 (TRPV4), an osmo- and mechanosensitive channel was expressed in the OHCs by means of immunohistochemistry. 4alpha-phorbol 12,13-didecanoate, a TRPV4 synthetic activator, induced NO production in OHCs. These results suggest that hyposmotic stimulation can induce NO production by the [Ca2+]i increase, which is presumably mediated by the activation of TRPV4 in OHCs. NO conversely inhibits the Ca2+ response via the NO-cGMP-PKG pathway by a feedback mechanism.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Animals; Calcium; Carbazoles; Cell Size; Cells, Cultured; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Enzyme Inhibitors; Gadolinium; Guanylate Cyclase; Guinea Pigs; Hair Cells, Auditory, Outer; Hypotonic Solutions; Indoles; Kinetics; Membrane Potentials; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Organ of Corti; Osmotic Pressure; Phorbol Esters; Potassium; Purinergic P2 Receptor Antagonists; Receptors, Purinergic P2; S-Nitroso-N-Acetylpenicillamine; Signal Transduction; Sodium Chloride; Suramin; TRPV Cation Channels

Lipopolysaccharides (LPSs) are thought to be one of the triggers of organ reactions to sepsis, which causes hepatocellular dysfunction. This dysfunction can be demonstrated by a reduction of organic anion transport. The aim of our study was to assess whether the transport of indocyanine green (ICG) is affected by LPS, and whether Kupffer cells are involved.. Single-pass liver perfusion with ICG at a concentration of 57.8 mg/kg/min was performed for 130 min. pH, oxygen tension and perfusion pressure were continuously measured in influent and effluent. Taurocholate was infused at 48.3 mg/kg/min to achieve a stable bile flow. LPS was added at concentrations of 0.45, 0.9 and 1.44 mg/kg/min for 30 min. ICG was determined photometrically in perfusate and bile. To depress the function of Kupffer cells male Wistar rats were treated with GdCl3 24 h in advance. Primary cultured hepatocytes were used for studying the direct effect of LPS on the uptake rate of ICG.. Forty-five minutes after administration of LPS a significant dose-dependent decrease of ICG uptake was seen in animals treated with LPS. Livers of animals pretreated with GdCl3 did not show this decrease. LPS had no direct effect on the uptake of ICG into primary cultured hepatocytes, whereas treatment of these cells with 8-bromo-cGMP resulted in a significant increase of ICG uptake.. LPS has a rapid dose-dependent effect on the detoxification properties of the liver for ICG. The rapid effect of LPS on ICG uptake in hepatocytes is mediated by Kupffer cells.

Topics: Animals; Cells, Cultured; Cyclic GMP; Dose-Response Relationship, Drug; Gadolinium; Indocyanine Green; Kupffer Cells; Lipopolysaccharides; Liver; Male; Phagocytosis; Rats; Rats, Wistar