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Biomedical subjects

S Moncada

Publications and source records attributed to S Moncada.

At least 451 records · Page 25Linked to original sources
PubMed1979

Prostacyclin eliminates the bioincompatibility of charcoal haemoperfusion.

During charcoal haemoperfusion (CHP) in dogs, use of prostacyclin (PGI2) in addition to heparin reduced the loss of platelets (25 +/- 6 vs 83 +/- 2%), the formation of platelet aggregates as judged by screen filtration pressure (65 +/- 6 vs 249 +/- 25mm Hg) and fibrinogen consumption (20 +/- 5 vs 46 +/- 6%). Prostacyclin also delayed neutralisation of heparin during CHP. This improvement of biocompatibility may now allow a proper assessment of CHP in liver failure.

Animals↗
PubMed1978

Prostacyclin can replace heparin in haemodialysis in dogs.

Despite the use of heparin, activation of platelets on the artificial surface of dialyser membranes results in thrombus formation, microembolisation, and thrombocytopenia. To assess the effects on these events of prostacyclin, the most potent inhibitor of platelet aggregation yet discovered, three groups of healthy greyhounds were dialysed with heparin, heparin plus prostacyclin, or prostacyclin alone. Prostacyclin, either alone or with heparin, abolished microembolisation from the dialyser (as estimated by whole-blood screen filtration pressure) and prevented thrombocytopenia. With prostacyclin, dialysis could be carried out without heparin, and there was no clotting of blood within the extracorporeal circuit nor any change in tests of coagulation.

Animals↗
PubMed1978

Eicosapentaenoic acid and prevention of thrombosis and atherosclerosis?

Unlike arachidonic acid (eicosatetraenoic acid, C20:4omega-6, A.A.), eicosapentaenoic acid (C20:5omega-3, E.P.A.) does not induce platelet aggregation in human platelet-rich plasma (P.R.P.), probably because of the formation of thromboxane A3 (T.X.A3) which does not have platelet aggregating properties. Moreover, E.P.A., like A.A., can be utilised by the vessel wall to make an anti-aggregating substance, probably a delta17-prostacyclin (P.G.I3). This finding suggests that, in vivo, high levels of E.P.A. and low levels of A.A. could lead to an antithrombotic state in which an active P.G.I3 and a non-active T.X.A3 are formed. Eskimos have high levels of E.P.A. and low levels of A.A. and they also have a low incidence of myocardial infarction and a tendency to bleed. It is possible that dietary enrichment with E.P.A. will protect against thrombosis.

Arachidonic Acids↗
PubMed1978

Dipyridamole and other phosphodiesterase inhibitors act as antithrombotic agents by potentiating endogenous prostacyclin.

The antithrombotic effect of dipyridamole is through phosphodiesterase inhibition and depends on stimulation of platelet cyclic A.M.P. by circulating prostacyclin in the bloodstream. Low doses of aspirin selectively inhibit platelet cyclooxygenase and potentiate the antithrombotic effects of dipyridamole and theophylline. High doses of aspirin also prevent prostacyclin formation, thereby abolishing the effects of dipyridamole. Thus, the antithrombotic effectiveness of the combination of aspirin and dipyridamole depends critically on the doses used.

Animals↗
PubMed1978

Vascular actions of arachidonic acid and its metabolites in perfused mesenteric and femoral beds of the dog.

The effects of arachidonate and its major metabolites were examined in vascular beds perfused via the femoral and mesenteric arteries of chloralose-anaesthetised dogs. Close intra-arterial injection of prostacyclin (PGI2, 0.02--2 microgram), PGE2 (0.05--1 microgram) and their precursors, the endoperoxide PGH2 (0.5--2 microgram) and sodium arachidonate (100--550 microgram), all induced vasodilatation. Sodium linoleate (500 microgram) was inactive. Prostacyclin was equally active in both vascular beds, but PGE2 was more potent in the femoral and less so in the mesenteric bed. PGH2 was of similar potency to prostacyclin in both beds, but 6-oxo-PGF 1 alpha (10--100 microgram) was inactive. Thromboxane A2 (TXA2, 1--2 microgram) was a potent vasoconstrictor of the mesenteric bed, but not the femoral bed, although the endoperoxide analogue U46619 was vasocontrictor in both vasculatures. Fatty acid hydroperoxides did not specifically modify the vasodilator effects of PGH2 or arachidonate, presumably because these inhibitors are rapidly reduced in vivo. Indomethacin and meclofenamate potentiated vasodilatation induced by prostacyclin or endoperoxide, but reduced or abolished that caused by arachidonate. The rise in perfusion pressure induced by TXA2 was potentiated and prolonged by indomethacin. Inhibition of synthesis of endogenous prostacyclin, by exacerbating the vasoconstrictor action of TXA2, may have contributed to this effect.

Animals↗
PubMed1978

Further studies on the enzymatic conversion of prostaglandin endoperoxide into prostacyclin by porcine aorta microsomes.

A simple, rapid radiochemical assay for prostacyclin synthesis has been used to characterize the enzyme in arterial walls which converts prostaglandin endoperoxides to prostacyclin. The enzyme displays a broad pH optimum, and catalyses a rapid conversion of saturating concentrations of the endoperoxide at 37 degrees C. Hydroperoxides of several unsaturated fatty acids are potent inhibitors of the enzyme, and act in a time dependent manner. The isomerase which converts prostaglandin endoperoxides to prostaglandin E2 or D2 was not detected in the arterial wall.

Animals↗
PubMed1978

Transformation of arachidonic acid and prostaglandin endoperoxides by the guinea pig heart. Formation of RCS and prostacyclin.

The metabolism of arachidonic acid (AA) was studied in perfused isolated hearts from guinea pigs. The coronary effluent was continuously bioassayed for prostaglandin-like substances (PLS) using the cascade technique of Vane. Injections of AA in doses between 1--50 microgram into the perfusion fluid prior to the heart produced vasodilatation of the coronary vascular bed followed by a contraction of the rat stomach strip (RSS), chick rectum (CR) and rat colon (RC) as well as relaxation of the bovine coronary artery (BCA). At the higher doses of AA there was also contraction of the rabbit aorta (RbA). The same pattern of effects on the bioassay tissues was seen when prostaglandin endoperoxide (PGH2) was perfused through the heart. The response of the bank of superfused tissues provided evidence for the formation of prostacyclin (PGX or PGI2), PGE2 and PGF2alpha. Chromatographic studies showed that 6-oxo-PGF1alpha together with other prostaglandins was present in the perfusate after acidification, which suggested that the bovine coronary relaxing substance consists mainly of PGI2. Moreover, the rabbit aorta contracting substance (RCS) released in the perfusate was due to prostaglandin endoperoxides and not to thromboxane (TXA2). The formation of PLS from AA was completely blocked after treatment of the heart with the cyclo-oxygenase inhibitors, indomethacin or meclofenamic acid. Pretreatment of the heart with 15-hydroperoxyarachidonic acid (15-HPAA), a selective inhibitor of prostacyclin synthetase, inhibited the effect of AA on the coronary vasculature and diverted the metabolic transformation of AA towards PGE2 and PGF2alpha.

Animals↗
PubMed1978

Inflammatory effects of prostacyclin (PGI2) and 6-oxo-PGF1alpha in the rat paw.

In the rat paw prostacyclin was 5--10 times less potent than PGE2 in causing oedema, and 5 times less potent in potentiating carrageenin-induced oedema, which it did in a dose-related manner. Prostacyclin was 5 times more potent than PGE2 in producing hyperalgesia and as potent as PGE2 in restoring carrageenin-induced hyperalgesia. The effects on oedema were longer lasting than those on hyperalgesia. 6-oxo-PGF1alpha was 500 times less potent than PGE2 in causing oedema by itself and in potentiating carrageenin-induced oedema. It had no hyperalgesic activity in this test.

Animals↗
PubMed1978

Enhancement of anaphylactic mediator release from guinea-pig perfused lungs by fatty acid hydroperoxides.

Fragments of chopped lung from indomethacin treated guinea-pigs had an anti-aggregating effect when added to human platelet rich plasma (PRP), probably due to the production of prostacyclin (PGI2) since the effect was inhibited by 15-hydroperoxy arachidonic acid (15-HPAA, 10 micrograms ml(-1)). Both 15-HPAA (1-20 micrograms ml(-1) min (-1)) and 13-hydroperoxy linoleic acid (13-HPLA, 20 micrograms ml(-1) min(-1)) caused a marked enhancement of the anaphylactic release of histamine, slow-reacting substance of anaphylaxis (SRS-A) and rabbit aorta contracting substance (RCS) from guinea-pig isolated perfused lungs. This enhancement was not reversed by the concomitant infusion of either PGI2 (5 micrograms ml(-1) min (-1)) or 6-oxo-prostaglandin F1alpha (6-oxo-PGF1alpha, 5 micrograms ml(-1) min(-1)). Anaphylactic release of histamine and SRS-A from guinea-pig perfused lungs was not inhibited by PGI2 (10 ng - 10 microgram ml(-1) min(-1)) but was inhibited by PGE2 (5 and 10 micrograms ml(-1) min (-1)). Antiserum raised to 5,6-dihydro prostacyclin (PGI1) in rabbits, which also binds PGI2, had no effect on the release of anaphylactic mediators. The fatty acid hydroperoxides may enhance mediator release either indirectly by augmenting thromboxane production or by a direct effect on sensitized cells. Further experiments to distinguish between these alternatives are described in the accompanying paper (27).

Anaphylaxis↗
PubMed1978

The mechanism of enhancement by fatty acid hydroperoxides of anaphylactic mediator release.

Indomethacin augmented the release of histamine and SRS-A but abolished synthesis of TxB2. Compound CLI that inhibited both cyclo-oxygenase and lipoxygenase pathways of arachidonic acid metabolism did not augment release of anaphylactic mediators. 13-HPLA enhanced mediator release from lungs in which arachidonic acid metabolism was blocked by compount CLI. Thus, it is concluded that 13-HPLA enhances mediator release not by altering the balance of arachidonic acid metabolites, e.g. by inhibiting synthesis of prostacyclin, but by a direct effect on lung mast cells. A corollary to this conclusion is that the fatty acid hydroperoxide (HPETE) formed by lipoxygenase from arachidonic acid may also augment the release of anaphylactic mediators. Thus, the enhancement of mediator release by indomethacin may be attributed to increased synthesis of HPETE following inhibition of cyclo-oxygenase.

Anaphylaxis↗
PubMed1978

Actions of prostacyclin (PGI2) and its product, 6-oxo-PGF1alpha on the rat gastric mucosa in vivo and in vitro.

The effects of prostacyclin (PGI2) and its breakdown product 6-oxo-PGF1alpha on various aspects of gastric function were investigated in the rat. PGI2 increased mucosal blood flow when infused intravenously. PGI2 was a more potent inhibitor of gastric acid secretion in vivo than PGE2. Like PGE2, PGI2 inhibited acid secretion from the rat stomach in vitro. PGI2 had comparable activity to PGE2 in inhibiting indomethacin-induced gastric erosions. Thus prostacyclin shares several of the activities of PGE2, and may be involved in the regulation of gastric mucosal function.

Animals↗
PubMed1978

An antiserum to 5,6-dihydro prostacyclin (PGI1) which also binds prostacyclin.

An antiserum was raised in rabbits using 5,6-dihydro prostacyclin, a stable analogue of prostacyclin, as the hapten, conjugated to bovine serum albumin. When added to platelet rich plasma the antiserum neutralised the inhibitory activity of prostacyclin, prostaglandin E1 and D2. The amount of antiserum required to neutralise completely a dose of prostacyclin giving 90-95% inhibition of ADP induced aggregation was 10-30 times less than that required for the other two prostaglandins. Small amounts of antiserum prevented the inhibitory activity of prostacyclin generated from endothelial cells in platelet rich plasma.

Animals↗