Differential release of eicosanoids by bradykinin, arachidonic acid and calcium ionophore A23187 in guinea‐pig isolated perfused lung

1 Release of endothelium derived relaxing factor (EDRF) and prostacyclin (PGO2) from endothelial cells (EC) cultured from bovine aortae was measured by bioassay and radioimmunoassay, respectively, during infusions (10min) of bradykinin (BK), adenosine diphosphate (ADP), arachidonic acid (AA), alkaline buffers and the free-bases (FB) of L-arginine or D-arginine. Release of EDRF from the luminally perfused rabbit aorta was also measured during infusions (10 min) of acetylcholine (ACh), substance P and ADP. 2 Bradykinin (10 or 30 nM) infused through the column of EC induced release of both EDRF and PGO2, neither of which was maintained for the duration of the infusion. 3 ADP (1.6 or 4pM) infused through the column of EC induced release of a EDRF which was maintained for the duration of the infusion and a release of PGO2 which lasted for a much shorter period. 4 Arachdonic acid (30 or 90 pM) infused through the column of EC caused a sustained release of EDRF and PGI2, both of which outlasted the infusion of AA.

Section: Discussionmentioning

confidence: 53%

Different patterns of release of endothelium‐derived relaxing factor and prostacyclin

Mitchell¹,

Nucci²,

Warner³

et al. 1992

“…The release of EDRF induced by both Bk and A23187 is temporally similar to the release of prostanoids induced by infusions of these agents into guineapig isolated lungs. Release induced by Bk is rapid, short-lasting and disappears during the infusion (Palmer et al, 1973;Bakhle et al, 1985) while that induced by A23187 is slow, long-lasting and reaches a peak several minutes after the end of the infusion (Bakhle et al, 1985). A23187 is generally considered to be the most potent releaser of prostacyclin and EDRF from vascular endothelium (Peach et al, 1985).…”

Section: Discussionmentioning

confidence: 99%

Bioassay of prostacyclin and endothelium‐derived relaxing factor (EDRF) from porcine aortic endothelial cells

Gryglewski

Moncada

Palmer

1986

Self Cite

217

A cascade superfusion technique has been developed for the differential bioassay of prostacyclin and endothelium-derived relaxing factor (EDRF) released from porcine aortic endothelial cells cultured on microcarriers, packed into a column and perfused. 2 Bradykinin (Bk; 20-100 nM) released prostacyclin (9.6 ± 1.5 nm per 106 cells; mean ± s.e.mean, n = 9) and prostaglandin E2 (PGE2; 2.1 ± 0.6 nm per 10' cells) from the column measured by relaxation of strips of bovine coronary artery (BCA) and rabbit mesenteric or coeliac artery, respectively. The presence of these prostanoids in the effluent was confirmed by specific radioimmunoassays. 3 A23187 (500-2000nM) also released both prostacyclin and PGE2 from the cells. This release was long-lasting and not reproducible. 4 Bk (20-100 nM) and A23187 (30-300 nM) released EDRF from the column. This was detected in a cascade of four rabbit aortic strips (RbA), denuded of endothelium and contracted with U46619 or phenylephrine. The relaxation of the RbA strips caused by EDRF was progressively attenuated down the cascade (half-life < 7 s) and was not affected by indomethacin. 5 EDRF and prostacyclin could be differentially bioassayed in a cascade of alternating RbAs and BCAs as prostacyclin did not relax RbAs and the time delay to the BCAs destroys EDRF. EDRF could be bioassayed on its own when the endothelial cells were treated with indomethacin. 6 5-Hydroxytryptamine 0.2, noradrenaline 1.0, platelet-activating factor (Paf-acether) 1.0, formylmethionyl-leucyl-phenylalanine 1.0, acetylcholine 0.5, bethanecol 0.5, adenosine diphosphate 0.25 and angiotensin II 0.1 gM did not release either prostanoids or EDRF from the column.

“…It is well established that PGI2 decreases coronary flow in isolated hearts from rabbits, rats and guineapigs and that PGI2 generation is increased by a range of stimuli including exogenous arachidonic acid (Schror et al, 1978;Belo & Talesnik, 1982), hypoxia (Wennmalm, 1979), Paf (Piper & Stewart, 1986) and ATP (Fleetwood & Gordon, 1987). Since the ability of both bradykinin and the ionophore, A23187, to stimulate PGI2 generation from cultured endothelial cells (McIntyre et al, 1985;Gryglewski et al, 1986;Gerritsen, 1987) and isolated perfused lungs (Bakhle et al, 1985) is well recognized, it was important to determine whether these stimuli had a similar effect in the perfused heart and also to identify a possible contribution to the observed vasodilator responses. Even though both Bk and A23187 elicited an increase in the generation of PGI2 over the same dose-range giving a dose-related decrease in perfusion pressure, indomethacin, which prevented PGI2 generation, failed to alter the magnitude of the vasodilator response.…”

Section: Discussionmentioning

confidence: 99%

Vasodilator actions of acetylcholine, A23187 and bradykinin in the guinea‐pig isolated perfused heart are independent of prostacyclin

Stewart

Piper

1988

1 The involvement of prostacyclin (PGI2) in the vasodilator responses to acetylcholine (ACh), A23187 and bradykinin (Bk) has been investigated in guinea-pig, isolated, Krebs-perfused hearts. 2 ACh (0.01-lOnmol), A23187 (0.1-1.Onmol) and Bk (0.3-lOpmol) each elicited dose-related and shortlasting (-2 min) reductions in perfusion pressure. Larger maximal responses were obtained in preparations with coronary vascular tone elevated by platelet-activating factor (100 pmol) than in preparations at basal perfusion pressure. 3 Bk and A23187 elicited dose-related increases in the generation of PGI2 as measured by its chemically-stable breakdown product, 6-oxo-PGFg. Indomethacin (2.8 uM) prevented both basal and the stimulated generation of 6-oxo-PGF,., whereas the magnitudes of the vasodilator responses were unaffected. 4 Attempts to identify the release of vasodilator materials by on-line superfusion bioassay of cardiac effluent were unsuccessful, indicating a possible role for a labile vasodilator such as endothelium-dependent relaxing factor (EDRF). In addition, the inhibitors of EDRF action/ production, mepacrine (3yM) or diethylcarbamazine (300pM), attenuated vasodilator responses to ACh without altering those to the endothelium-independent vasodilator, verapamil (1 nmol). 5 Haemoglobin (10pM) reduced vasodilator responses to ACh, Bk and verapamil and abolished those induced by A23187. Inhibition of the endothelium-independent vasodilator, verapamil, was significantly less than that for the other compounds. 6 The present data indicate the existence of an indomethacin-resistant vasodilator mechanism in the coronary microcirculation in response to ACh, A23187 and Bk. EDRF is a candidate for mediating these responses; however, a direct vasodilator action of these substances cannot be excluded.