8-bromocyclic-gmp and diethylamine

The effects of the Pseudomonas aeruginosa virulence factor pyocyanin (PCN) on the contractile function of porcine coronary arteries was investigated in vitro. Artery rings (5 mm) were suspended in organ baths containing Krebs' solution for the measurement of isometric tension. The effect of PCN on resting and precontracted coronary arteries was initially investigated with various agents. Arteries were precontracted with prostaglandin (PG) F2α or potassium chloride and endothelium-dependent relaxations were induced by various agents in the presence of PCN. Pyocyanin (0.1-10 μmol/L) evoked small-amplitude, dose-dependent contractions in resting porcine coronary arteries. In addition, PCN amplified the contractile response to PGF2α , but did not alter responses to carbachol. Pyocyanin (0.1-10 μmol/L) significantly inhibited endothelium-dependent relaxations evoked by neurokinin A. Pyocyanin also inhibited relaxations evoked by diethylamine nitric oxide (a nitric oxide donor), forskolin (an adenylate cyclase activator), dibuytyryl-cAMP (a cAMP analogue), 8-bromo-cGMP (a cGMP analogue) and P1075 (a KATP channel activator), but not isoprenaline (β-adrenoceceptor agonist). These results indicate that physiological concentrations of PCN interfere with multiple intracellular processes involved in vascular smooth muscle relaxation, in particular pathways downstream of nitric oxide release. Thus, PCN may alter normal vascular function in patients infected with P. aeruginosa.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Animals; Colforsin; Coronary Vessels; Cyclic AMP; Cyclic GMP; Diethylamines; Dinoprost; Female; Isoproterenol; Male; Muscle Contraction; Muscle Relaxation; Nitric Oxide; Pseudomonas aeruginosa; Pyocyanine; Swine; Vasodilation

To characterise the inotropic response of isolated myocytes to a range of structurally unrelated NO donors and to assess the role of NO release kinetics, NO species and cyclic nucleotides in mediating the observed changes.. Guinea-pig (GP) and human myocytes were prepared by enzymatic digestion. Paced contractile amplitude was recorded at 37 degrees C. NO release was measured by reduction of oxyhaemoglobin and using an NO electrode. Cyclic nucleotides were measured using a tritium labelled competitive binding assay.. The NO donors S-nitrosoglutathione (GSNO) and diethylamine/NO (DEA/NO) produced positive inotropic effects in GP myocytes at (10(-5) M) (25 and 111% increases of contraction amplitude). The response to GSNO was significantly enhanced in the presence of a low concentration of isoprenaline (3x10(-10) M). Positive inotropy was observed with a range of both thiol and non-thiol donors, amongst which a fast rate of NO release was associated with positive inotropy. The response to GSNO was abolished by the free NO scavenger oxyhaemoglobin, but not by ODQ (soluble guanylyl cyclase [sGC] inhibitor), Rp-cAMPS (protein kinase A inhibitor) or thapsigargin (sarcoplasmic reticulum Ca(2+) uptake blocker). Direct measurement of cyclic nucleotides showed a rise in cGMP but not cAMP. Human ventricular myocytes showed a significant increase of contraction with GSNO (48+/-15.8%, n=7, P<0. 05) in the presence of isoprenaline and a marked response to DEA/NO alone.. Isolated GP and human myocytes show a positive inotropic effect with certain NO donors. This is independent of sGC and cAMP. The rate of NO release from donors appears important in mediating the effect.

Topics: Animals; Cardiotonic Agents; Cells, Cultured; Cyclic AMP; Cyclic GMP; Diethylamines; Dose-Response Relationship, Drug; Glutathione; Guinea Pigs; Humans; Isoproterenol; Male; Myocardial Contraction; Myocardium; Nitric Oxide; Nitric Oxide Donors; Nitroso Compounds; Penicillamine; S-Nitrosoglutathione; Stimulation, Chemical