Effect of anti-inflammatory compounds on actomyosin-adenosinetriphosphate interaction

Involvement of K+ channel permeability changes in the L-NAME and indomethacin resistant part of adenosine-5'-O-(2-thiodiphosphate)-induced relaxation of pancreatic vascular bed

1. We have previously demonstrated that adenosine-5'-O-(2-thiodiphosphate) (ADPbetaS), a potent P2Y-purinoceptor agonist, relaxed pancreatic vasculature not only through prostacyclin (PGI2) and nitric oxide (NO) release from the endothelium but also through other mechanism(s). In this study, we investigated the effects of an inhibitor of the Na+/K+ pump, of ATP-sensitive K+ (K(ATP)) channels and of small (SK(Ca)) or large (BK(Ca)) conductance Ca2+-activated K+ channels. Experiments were performed at basal tone and during the inhibition of NO synthase and cyclo-oxygenase. 2. In control conditions, ADPbetaS (15 microM) induced an initial transient vasoconstriction followed by a progressive and sustained vasodilatation. In the presence of N(omega)-nitro-L-arginine methyl ester (L-NAME, 200 microM) the transient vasoconstriction was reversed into a one minute vasodilator effect, which was then followed by a progressive and sustained vasodilatation similar to that observed with ADPbetaS alone. The addition of indomethacin (10 microM) did not significantly modify the profile of ADPbetaS-induced vasodilatation. 3. Ouabain (100 microM) decreased basal pancreatic flow rate and did not modify ADPbetaS-induced relaxation. This inhibitor of the Na+/K+ pump increased the pancreatic vasoconstriction induced by L-NAME or by the co-administration of L-NAME and indomethacin. Ouabain did not modify either the L-NAME or the L-NAME/indomethacin resistant part of the ADPbetaS vasodilatation. 4. The K(ATP) inhibitor tolbutamide (185 microM) did not significantly modify basal pancreatic flow rate and ADPbetaS-induced relaxation. This inhibitor which did not change L-NAME-induced vasoconstriction, significantly diminished the L-NAME resistant part of ADPbetaS-induced vasodilatation. Tolbutamide intensified the vasoconstriction induced by the co-administration of L-NAME and indomethacin. In contrast, the L-NAME/indomethacin resistant part of ADPbetaS vasodilatation was not changed by the closure of K(ATP). 5. The SK(Ca) inhibitor apamin (0.1 microM) did not significantly change pancreatic vascular resistance whatever the experimental conditions (in the absence or in presence of L-NAME or L-NAME/indomethacin). In the presence of L-NAME, the closure of SK(Ca) channels changed the one minute vasodilator effect of ADPbetaS into a potent vasoconstriction and thereafter modified only the beginning of the second part of the L-NAME-resistant part of the ADPbetaS-induced vasodilatation. In contrast, the L-NAME/indomethacin resistant part of ADPbetaS-induced relaxation remained unchanged in the presence of apamin. 6. Charybdotoxin (0.2 microM), an inhibitor of BK(Ca), increased pancreatic vascular resistance in the presence of L-NAME/indomethacin. In the presence of L-NAME, the closure of BK(Ca) channels reversed the one minute vasodilator effect of ADPbetaS into a potent vasoconstriction and drastically diminished the sustained vasodilatation. In contrast the L-NAME/indomethacin resistant part of ADPbetaS-induced relaxation was not modified by the presence of charybdotoxin. Under L-NAME/indomethacin/charybdotoxin/apamin infusions, ADPbetaS evoked a drastic and transient vasoconstriction reaching a maximum at the second minute, which was followed by a sustained increase in the flow rate throughout the ADPbetaS infusion. The maximal vasodilator effect of ADPbetaS observed was not modified by the addition of apamin. 7. The results suggest that the L-NAME-resistant relaxation induced by ADPbetaS in the pancreatic vascular bed involves activation of BK(Ca), K(ATP) and to a lesser extent of SK(Ca) channels, but the L-NAME/indomethacin resistant part of ADPbetaS-induced relaxation is insensitive to the closure of K(ATP), SK(Ca) and BK(Ca) channels.

Study of the mechanisms involved in adenosine-5'-O-(2-thiodiphosphate) induced relaxation of rat thoracic aorta and pancreatic vascular bed

1. The endothelium-dependent relaxation of blood vessels induced by P2Y-purinoceptor activation has often been shown to involve prostacyclin and/or nitric oxide (NO) release. In this work, we have investigated the mechanisms involved in the relaxant effect of the P2Y agonist, adenosine -5'-O-(2-thiodiphosphate) (ADP beta S) using two complementary preparations: rat pancreatic vascular bed and aortic ring. 2. On the pancreatic vascular bed, ADP beta S (1.5 and 15 microM) infused for 30 min induced a concentration-dependent vasodilatation; it was progressive during the first 10 min (first period) and sustained from 10 to 30 min (second period). Indomethacin (10 microM) delayed ADP beta S-induced vasodilatation (1.5 and 15 microM) by about 6 min. N omega-nitro-L-arginine methyl ester (L-NAME) (200 microM) suppressed the relaxation for about 5 min but thereafter ADP beta S at the two concentrations progressively induced an increase in the flow rate. Even the co-administration of L-NAME and indomethacin did not abolish the ADP beta S-induced vasorelaxation. 3. On 5-hydroxy tryptamine (5-HT) precontracted rings mounted in isometric conditions in organ baths, we observed that ADP beta S induced a concentration-dependent relaxation of rings with a functional endothelium; this effect was stable for 25 min. The ADP beta S relaxant effect was strongly inhibited by Reactive Blue 2 (30 microM) and was suppressed by pretreatment of rings with saponin (0.05 mg ml-1 for 30 min), which also abolished the acetylcholine-induced relaxation. 4. ADP beta S-induced relaxation of 5-HT precontracted rings is largely inhibited by indomethacin (100 or 10 microM) or L-NAME (100 microM). 5. We conclude that: the ADP beta S-induced relaxation is endothelium-dependent, mediated by P2Y-purinoceptors, and at least in part linked to NO and prostacyclin release, depending on the preparation used. Furthermore, on the pancreatic vascular bed, (an)other mechanism(s) than prostacyclin and NO releases may be involved in ADP beta S-induced vasodilatation.

Effect of indomethacin on the injection-abortion interval of 15(S) 15 methyl PGF2 alpha-induced mid-trimester abortions--a randomized study

There have been conflicting reports on the effect of non-steroidal anti-inflammatory drugs on the abortifacient effect of prostaglandins. The efficacy of intra-amniotic 1.5 mg 15(S) 15 methyl PGF2 alpha (15 me PGF2 alpha) in terminating mid-trimester pregnancy in 10 subjects has been compared with the effect of the same medication given to 10 others who had had indomethacin 25 mg and 50 mg orally three and one hour before the PG administration. In the subjects who had the PG analogue only the injection-abortion interval was 17.0 hours. This was significantly shorter (P less than 0.01) than in those who had also received indomethacin (25.4 hours).

Cardiac electrophysiologic effect of indomethacin

The anti-inflammatory agent indomethacin has been shown to antagonize calcium in smooth muscle. This study looked at indomethacin's effect on ventricular muscle and conduction tissue. Indomethacin shortened the duration of the action potential plateau in the tissue studied. This was probably a result of its interference with transmembrane calcium movement.

Evidence against the involvement of prostaglandins in the vasoconstrictor action of calcium ion in rat mesenteric blood vessels

1. Prostaglandin E2 (PGE2) has been claimed to be essential to the vasoconstrictor action of noradrenaline in rat mesenteric blood vessels. Since noradrenaline acts by releasing intracellular calcium, experiments have been performed using the perfused rat superior mesenteric artery preparation to determine whether prostaglandin synthesis is necessary for the direct vasoconstrictor action of calcium. 2. The cyclo-oxygenase inhibitors, indomethacin and 5,8,11,14-eicosatetraynoic acid (ETA), inhibited responses to noradrenaline and calcium but both were less effective in inhibiting the response to calcium than to noradrenaline. 3. PGE2 (6 ng-20 micrograms/ml) failed to overcome the inhibitory effect of indomethacin (62 micrograms/ml) and ETA (10 micrograms/ml) on the response to the EC50 of Ca2+ (100 micrograms/ml). The EC50 of Ca2+ did not significantly increase PGE2-like release by the blood vessels from the resulting value of 19 +/- 8 pg of PGE2 equivalents/min. 4. PGA1 (6 micrograms/ml) and the thromboxane A2 agonist, U-46619 (200 ng/ml), both caused full restoration of indomethacin-depressed responses to calcium, but did not restore responses depressed by ETA. U-46619 (200 ng/ml) also reversed the inhibitory effect of papaverine (4 micrograms/ml) and caused a 1.6 fold potentiation of Ca2+ responses. 5. The results do not support the hypothesis that prostaglandin synthesis is essential to the vasoconstrictor action of Ca2+ in rat mesenteric blood vessels.

The effect of the phenyl phosphonate N-0164 on prostaglandin action and on post inhibitory excitation in the taenia of guinea-pig caecum

In the taenia of guinea-pig caecum, electrical stimulation of the non-adrenergic inhibitory nerves caused relaxation which was followed by an after-contraction. The purinergic compount ATP (10(-5) M) also produced muscle relaxation while wash-out was associated with an after-contraction. The role of prostaglandins (E1, E2, F1 alpha, F2 alpha; 10(-9)--10(-6 M) in these contractions was studied. The prostaglandin responses reflected by membrane depolarization (E type) and muscle contraction (E and F type) were inhibited by the phenyl phosphonate N-0164 (10(-5) M). This substance did not affect the membrane potential or the nerve-mediated non-adrenergic inhibitory junction potential (IJP). The effect of N-0164 on the muscle cells could account for the limited reduction of the after-depolarization and contraction following electrical stimulation. The ATP after-contraction, however, could be inhibited completely by N-0164. The results are consistent with the possibility that the ATP after-contraction was produced by E type prostaglandins, while involvement of prostaglandins in post inhibitory excitation following nerve stimulation seems unlikely.

Adenosine triphosphate-induced contractile process in rat lymphocytes and its inhibition by anti-inflammatory agents

Addition of adenosine triphosphate to glycerol-treated rat lymphocytes produced characteristic cytoplasmic movements. These were inhibited or prevented by low concentrations of acetylsalicylic acid, phenylbutazone and indomethacin.

Mechanism of the inhibitory action of indomethacin on smooth muscle

1. Strips of muscle from the wall of the guinea-pig stomach contracted in response to electrical field stimulation (100 ms pulses, 0.2 Hz) or to histamine (1 mug/ml), and these responses were inhibited by indomethacin (2-20 mg/100 ml).2. Glycerol-extracted strips of stomach muscle developed tension when exposed to a mixture of ATP, CP, magnesium chloride and calcium chloride. The tension response was not altered by indomethacin (50 mg/100 ml).3. Indomethacin failed to alter the content of ATP or of CP in strips of stomach muscle.4. The calcium content of strips of stomach muscle increased in response to 30 min of electrical stimulation (100 ms pulses, 0.2 Hz). The uptake of calcium and the contraction of the strips were inhibited by indomethacin (2-20 mg/100 ml) to a similar extent.5. Calcium uptake by electrically stimulated guinea-pig aorta was inhibited by lower concentrations of indomethacin than were required by stomach muscle.